You also don't need to make every enemy an idiot like a videogame. Monk catches an arrow? Archer wastes a turn figuring that out, calls it out to his teammates start of next turn and targets someone else.

A green dragon, depending on your source books, should be more than smart enough to notice its breath attack didn't work on someone and change tactics.

It doesn't work in every situation, like with enemies that shouldn't be smart enough to figure it out, but there's some great room for fun reminding your players that the enemies aren't always braindead.

It also can add an extra layer to combat. Take out the commander that's noticing this stuff to prevent it. Kill the archer before he can call out the monk caught his arrow, so another archer wastes a turn.