Tactics are up to the DM...and even an animal with low intelligence will have enough cunning to make effective use of their abilities.

I would temper that though by avoiding DM-metagaming: In other words, if it isn't obvious that a character is the prime 'healer' then I would not recommend that a low-intelligence monster aim to cut them off first (is it that easy to distinguish a cleric from a fighter before they act?)

On the other hand, a more intelligent foe could reasonably be expected to adjust their tactics based on character abilities (and a good way of making an especially intelligent foe such as a beholder or mindflayer even scarier is to assume that they have learnt the characters strengths and weaknesses and this knowledge against them).

Tactics are up to the DM...and even an animal with low intelligence will have enough cunning to make effective use of their abilities.

I would temper that though by avoiding DM-metagaming: In other words, if it isn't obvious that a character is the prime 'healer' then I would not recommend that a low-intelligence monster aim to cut them off first (is it that easy to distinguish a cleric from a fighter before they act?)

On the other hand, a more intelligent foe could reasonably be expected to adjust their tactics based on character abilities (and a good way of making an especially intelligent foe such as a beholder or mindflayer even scarier is to assume that they have learnt the characters strengths and weaknesses and use this knowledge against them).