my idea is that when a person in catas levels up, a flash appears around his character so the team knows he has leveled up

this could be useful specially for a mage, so the rest of the group knows that he has full mana again

vote please

not needed imo

I always keep an eye on my cata mates. Healer or no.

Plus you got the "xxxx has gained a lvl at the bottom of the screen" and the experience bar to show you he's about to lvl.

nn imo.