A few things I miss about XI;

Quantity of Spells for Mages
Weaponskills for Melees and Abilities of All Classes
and the over all uniqueness of each class.
I miss Skill Chaining in low level Groups.
Going into a Zone and the Mobs actually pose a threat.
Purchasing / Farming spells for Mages, Why are they just given to us?!
The Gear, may be, the #1 thing I miss. Not a fan of every piece being exactly the same as the piece before, just larger numbers.
The Auto-Translate function, so much better than what we currently have
Gear Comparison Windows, Why don't we have this?!

Things I don't Miss

Looking for party for 3 Hours, just to have to log off.
Over crowded HNM pops. Waiting for the 3 hour window to pass, just to Have someone in ur PT target a Darter and lose claim on Fafhogg.
Lack of Transportation between areas.

While I understand some of his has been addressed in recent Expansion, I stopped playing shortly after the 90 lv Cap.