Join a group? Except for
maybe Enchanters I don't think any class can solo the relevant mobs, because their HP/regen require DPS, but they hit hard enough that they also require slow/healing.
A (Torpor) shaman/monk duo can certainly do some giants though. I
think they could do some that drop Thurg armor ... but I haven't actually killed armor mobs with a monk myself (I've only done mobs like
Bjrakor the Cold), so YMMV.
In any case, you'll have to get more specific than just "caster" if you want useful responses.