Visual clarity is always extremely hard in these types of games and needs to be designed around from the beginning since everything plays a factor. From player abilities to monster abilities to area color.
One thing I would hope to see is a stronger coloration for “blue” and “yellow” monsters. Many other arpgs use the same trope but something like a shader could be applied to give the monster a blue or yellow glow/coloration.
Ideally, this should also be applied in some sense to boss monsters.