Amargas are not worth it for PVE at all. They're good for pvp, but for PVE it's not that good. Creatures don't stay in the little effect globe long enough, and I don't think direct hits do anything different anyways. If you're attacking a base, then accuracy doesn't really matter. Amargas are heavy support creatures/siege creatures, but there's really not much they can do against something in PVE. They could be viable in some boss fights where there's a bunch of minions. I've tried them in creative. Their utility as a traveling mount is essentially the only reason to tame one of them in PVE. They're decently fast, can swim, keep you warm or cold, and they can hold their own against most creatures, or run away.