How would a gnoll get hold of an acid arrow anyway? Using a bow and arrow is probably at the limits of their intelligence already. This annoyed me to no end on my playthrough.
I wondered about this myself. I imagine it'll be dealt with later; though feedback obviously helps. Overall the encounter was weird: I expected them to be much more bitey and much less... well, human.
This reminds me a small problem I have sometimes with these sorts of games. The fact that even when the AI is rather good, there's no active effort to make you feel the clear distinction between smart and stupid enemies.
You should be able to perceive the clear difference between fighting a party of enemy adventurers or, say, a pack of stupid beasts.
Back to the gnoll example, I noticed how they kept focus firing my weak caster on the back line instead of dealing with what was in front of them.
