This is more of a lore/thematic thing than a game mechanics thing (although it could certainly bleed over into that), but what the hell, one thing I'd like to see class-wise is for them to come up with a more fleshed-out idea of what a wizard is, in comparison to the other mage classes. I didnt play one in EQ1, but I did in EQ2, and it felt like...like wizards were defined by being the mages that didn't have any of the defining features of the other mage classes (summoning elementals, raising the undead, mind control, etc), but got to do the generic mage stuff better in exchange. There is a certain appeal in that, since I usually want to play a straight-up mage, and not an illusionist or pet user, but it'd still be nice if their was a more concrete idea of what a wizard is. The fact that their spell aesthetics have so much in common with the non-summoning spells of the magician/conjuror (as an aside, I prefer the name 'conjuror' for that class, it's more descriptive), really doesn't help matters.
I also kinda feel like warriors have a similar issue, being largely defined as, "the fighter class which doesn't have magic, or hunting and tracking skills, or kung fu, etc"; being defined by what they lack, rather than what they have.