I think it would be nice if for every five levels a character is given one stat improvment point to be permanently allotted as they wish. So at level 50 a player would essentially have been able to improve their character by a total of 10 stat points.
A stat point would essentially buy one to two percent more damage %, damage reduction %, targetting %, or the like and maybe X amount of additional health or mana points, all depending on where a player wishes to permanently allot their points. This would add more differentiation between players and hopefully allow players some sort of school specialization.
I've noticed that all the level 50th gear is essentially all the same on a school by school basis. I mean characters of the storm school with 50th level gear often have the same exact equipment as as all other level 50th storm players. I kind of hate this lack of equipment differentiation, and it would be nice to have more options, and I think stat points would help make different gear set ups a bit more differentiatable.