Deep trolls are pretty boring monsters. They do a lot of damage, but they feel a lot like “deep yaks”. I have some ideas for making them more interesting - keep them spawning in bands, but have “classed” deep trolls like you get with other enemies.
This page has been updated on 2012-08-26, using ideas from ##crawl-dev.
These would be kept, unchanged. Deep troll bands would consist almost entirely of this enemy.
These would act as band leaders. Their focus is on buffing spells. It should have haste other, heal other, and probably blink away. Smiting is a possibility, but only if the other spells aren't enough.
These would provide ranged support to deep troll bands. Their main attack spell would be LRD. They'd also have digging, and would use it offensively. The AI for digging should be improved, so these monsters widen corridors they are stuck in. This would also make deep troll bands more dangerous in corridors (the earth elementalists could dig squares next to you, for instance). If these two spells aren't enough, their spell list could be padded out with a dummy “melee” spell. This would probably be better than giving them a conj spell.
Sandblast would be thematic, if only for flavour. — evktalo 2012-08-29 11:53