No. It's not about lvl0->lvl1 only.
It's about all skills that are not used often.
If you want to cast haste, you need enchantment at relatively high level.
But if you don't need any other enchantment, you need to do cast something meaningless
every time there is exp in the pool.
No, you just have to cast an enchantment spell when there's XP in the pool - and that spell can be haste. No need for meaningless spells.
Have you ever tried to train fighting with caster?
Kill powerful foe with spell. Return to dungeon, find some weaklings,
swing with sharp piece of metal at them (you don't even need to kill them, just attack).
Repeat. At what point this isn't some perverted form of grinding?
I guess I don't see that as unrealistic or weird. A skilled magician gets battle experience while using magic, then tries physical combat on weaker enemies, because he's not sure of his new skill yet. And because skills can level up pretty quickly when you've got a big XP pool, it doesn't take that long - not grinding.
Example: I usually play an MDFi and aim to get a crossbow. These rarely show up before DL 10. When I get one, I wait till I have a big XP pool then I make sure I shoot the bow as often as possible, plunging all those points into the crossbow skill.
Also, you can turn off skills on the (m) screen, which means they won't train when you don't want them to, saving points for the skills you do want.
I don't really know why they didn't make training of combat spells by damaging
enemies and training of non-combat spells by usage only.
Non combat spells are trained by usage but the points that go into that training come from combat. The points have to come from somewhere - where if not combat, which is what Crawl is about?