That's curious - I tend to find ranged weaponry is *very* overpowered in roguelikes.
Take Nethack, for instance. You can machine-gun a stack of blessed daggers doing insane damage (even more damage than spells/melee) all of the game, and with almost all classes. You can check at r.g.r.n., one of the most advised strategies is to use that, with as much monsters as possible, since it is the less risky. In Angband, one of the easiest classes to use is the Ranger, doing absurdly high damage with his enchanted bow and arrows, while keeping yourself in safety (using Phase Doors when the enemy is too near)... even the Warriors have to use a bow or other ranged weapon for the tightest situations, to chip down an enemy's health with much less risk involved. Also, some melee enemies can destroy your equipment, which will *not* happen to you if you attack them from afar, and the ones who destroy equipment from afar will destroy that of the meleer too. If that wasn't enough, the status effect "Afraid" does not let you attack on melee, but it *lets you attack using ranged weaponry*. I think in Crawl this is the case too - meleeing is very dangerous, as you can die *quickly*, so it is always advised to soften up targets with either darts or, preferably, poisoned needles. Also, as always happens, meleers suffer from the "easy start, hard late-game" developers seem to love for them (just the contrary as spellcasters, which are very powerful later on)
So, I think the fact is ranged combat has it's intrinsic benefits - not having to risk yourself getting near an enemy/a group of enemies being the most obvious. And when enemies have brands or other special abilities that activate only on melee combat, the benefits of ranged weaponry are even higher. But it seems than in some roguelikes, to "balance" ranged and melee, forget that point and just boost damage on ranged, which leads to the fact that it is almost always the answer to everything.
Lately I am playing a lot of Angband, and I can tell you that I pick out all uniques and hard monsters with bow & arrows, at least until they get close enough for some more pain
Anyway, this post is just my opinion from what I've read and my own experiences, so it is not a consumated fact.