Yeah, I've got a huge list of suggestions.
I'm going to divide it into multiple sections to make it a bit more readable.
Items
My opinion of the current state of the game is that it's doing pretty well. It generates a nice number of weapons, armor, and potions, such that you usually do get what you need, you usually don't get everything you want, and you have to make decisions about what to carry and what to abandon.
The biggest problem with items that I see is that the difference between terrible weapons and great weapons isn't very large. A late game character with a dagger can inflict about 40 damage a hit, while that same character with a claymore can do about 60. That difference is meaningful, but it isn't nearly so large as the difference between good armor and bad armor. I've got an idea on how to help with this in the special attacks section below.
Monsters
Enemies could use a bit more variety. Most of the early game enemies are interchangeable with each other, and are not very threatening. Enemies that stand out to me are poisonous masses for their strength damage effect, mimics for their... mimicry, and demons and purple worms for their extreme threat levels.
I think the majority of early game enemies could use a boost to their attack power. Everything before beasts inflicts relatively small amounts of damage and doesn't need to be taken seriously (except poisonous masses). But beyond that, I feel that a good enemy should have something that makes them stand out from other enemy types. It should be something that changes the way the player deals with them, but without being tedious or unfair. So here are a few enemy suggestions I've got:
One or two enemies that move at double speed. Rodney doesn't seem to have a speed system like Angband and ADOM do, but it should be easy enough to simulate it by letting certain enemies move twice when their turn comes up. It would be an interesting addition to the game because it would be much more difficult to set up special attacks, and it would also make the wall jump perk more useful, since it'd let the player move around just as quickly as their opponent to either escape or set up a special attack.
Quasits seem like a good fit for this trait. I think it would be fun to give it to demons or purple worms as well to make something really scary. Maybe lower their health to compensate. Demons and purple worms are good in that they're enemy types that requires a lot of care and attention to deal with, but they're also very similar to each other, and I think something like this would help them stand out.
Another enemy that would be interesting and easy to implement would be an enemy with extremely high health, but less attack power than other enemies. Like, something that shows up around the same floor as orcs and has 10x the hit points of an orc, but only inflicts 1/3 as much damage as an orc. Golems would be a good thematic fit. The idea is that this is an enemy the player is encouraged to avoid rather than fight. The low attack power means taking one or two hits isn't a big deal, but their high hp means that avoiding any damage while fighting is basically impossible. This type of enemy would make the wall jump perk more attractive, since it helps with escaping, and it would also encourage players to pick up perks like rage so that direct confrontation becomes a more attractive option. I know that bullet sponges in games are not very popular (and rightly so), but combat in Rodney is fast paced and aggressive enough that even an enemy with 10x the health of an orc could probably go down in 5 or 6 hits. That isn't too bad.
Perks and Special Attacks
I think the parts of the game that have the most potential for improvement are the perk and special attack systems. They're already good now, but I think with a few changes they could be even better. The biggest problem is that there isn't very much encouraging players to try totally different builds. Every character is going to want Butcher, Crush, Raze, and Packer, and Corner is as good as every other special attack combined.
Most game developers seem think the best way to balance a game is to homogenize everything. My preferred method is to make every ability so awesome that your player enjoys every ability that they have, and longs for every ability they don't have. So rather than nerfing corner (which would make the game nearly impossible), I'm going to suggest improvements to existing perks, as well as new perks that should make the game more interesting.
Build Up - increase the damage multiplier to 4x damage. Cause heavy damage to the user's weapon (say, the equivalent to 10 normal attacks worth of durability).
I'm making this suggestion for two reasons. First, Build Up is very similar to Corner, but generally Corner is more useful. Improving its damage multiplier is the easiest way to give it value, and the weapon damage penalty exists to keep the extra damage from being overpowered.
The other issue this would address is the problem of weapons being the least valuable equipment type. A player in leather armor is very vulnerable, while a player in plate armor is nearly invincible. But on the other hand, a character with a dagger will end up inflicting about 2/3 as much damage as a player with a claymore, so there isn't a big incentive to gather a ton of weapons like there is with armor and potions. With this ability, the player would be able to severely damage one of their weapons in exchange for a get out of jail free card. This would make inventory management more interesting, since a large supply of weapons would be just as useful as other item types.
If this change is made, it would be important to make sure that whenever the player takes an action that could count as two special abilities, Build Up does not trigger. Say you've got a player skipping a turn and then attacking a cornered enemy. You'd want Corner to trigger, not Build Up, so the player doesn't accidentally destroy their weapon.
Riposte - Skip a turn adjacent to an enemy. If the enemy attacks, the player counterattacks with a 4x damage multiplier. (Perhaps it should require Build Up as a prerequisite?)
Another high damage ability to challenge Corner's domination. This one requires the player to take damage in exchange for getting to make a powerful attack in return. I don't think the 4x multiplier would make it overpowered, because the only way to survive in Rodney is to win most fights without taking any damage at all. Riposte would require the player to take a hit. Its main uses would be against lone, durable enemies like purple worms, and in desperate situations where the player finds themselves trapped without an adequate weapon. Riposte would also be a good choice for players who want to fight rather than avoid the golem enemies I suggested earlier.
Defensive Fighting - An attack that inflicts normal damage, but the user receives half damage for one turn. (Triggered by being attacked while your back is up against a wall? Or what about moving away from an enemy for one turn, then attacking?)
This one is different from all the current special attacks in the game, but I think it would be a good addition. Right now, most of the your effort in Rodney is directed towards killing enemies before they can land a hit on you. This move would be suited to the situations where that isn't possible. Usually it'd be a better idea to use a high damage attack to get an instant kill. But even though Defensive Fighting wouldn't be useful in most situations, it would be really good in a few certain places. And that's the kind of ability I like in tactical games. Things like that increase depth.
Let's say your character is capable of inflicting 15 damage, and you've got an opponent that has 40 hp. By attacking normally, you will kill them in three hits and receive at least two hits in return. If you use Corner you can kill them in two hits and will only take one hit in return. Spamming Defensive Fighting would mean you need to land three hits and receive two half damage hits, so it's exactly as good as Corner. But if you use Defensive Fighting for the first attack, and Corner for the second attack, you can get a kill in two hits and only receive half of the damage of a normal attack in total.
Courage - recover 1 hit point for defeating an enemy
Heroism - recover between 1 and 5 health for defeating enemies, the amount is based on enemy strength (requires Courage)
Rodney reminds me of Flend's DDRogue and PrincessRL 7DRLs, and one of the coolest items in those games is the life-draining glove. There perks are intended to simulate that effect. They'd encourage the player to completely explore levels, and would be useful for someone who has been having bad luck with potion drops.
Wanderer - recover 10 hit points for entering a new floor
Explorer - recover 25 hit points for entering a new floor (requires Wanderer)
Another set of alternate recovery methods. I don't think either of these would be game changers, but they'd be nice additions to any build.
Sweep - Increase damage to 150% of a normal attack.
Attacking multiple enemies for normal damage isn't terribly useful. Right now sweep is the equivalent to fighting multiple enemies one at a time in a hallway, and while in most roguelikes that's a good idea, it isn't enough in Rodney where you really need to oneshot as many foes as possible. 150% is enough to make it rewarding in situations where you're trapped in an open room, while still being low enough that it doesn't overwhelm other abilities.
Spin Slash - Attacks all enemies adjacent to the player for 150% damage. (Requires Sweep, triggered by using a normal attack while adjacent to more than one enemy)
Right now Spin Slash is a pretty bad ability. It requires you to stand where two enemies can hit you, it only hits one of them at a time, the first hit does no extra damage, and even when you meet all of those requirements, it's still not very impressive. Changing it to an upgraded version of Sweep would make it much more useful, especially when the player is surrounded by enemies in an open room, which is the most dangerous situation in the game. This would be especially useful for when you go down a set of stairs and the game spawns you somewhere dangerous.
Dang, that was longer than I wanted it to be. Well, hopefully it will be useful to you.
Edit:
Oh yeah, I meant to suggest that Slash and Backslash also inflict 1.5x damage for the same reasons as with Sweep.
