What do you mean eighteen equipment slots? They should structure D2 to be a true action-fpsmmorpg. Fewer characters but, deep individual progression for each(which includes a Wardrobe system, and for a solid developer is a no-brainer). No need for nine subclasses for a single character. Just expand the the functionality and form of each class and every aspect of them. Specifically their support abilities and functional roles as part of a group. Then, in turn, you structure your activities and challenges in game (dungeons, missions, quests, puzzles raids, campaigns etc.) to support players getting intelligent and creative in using all the tools in their bag to rocking through all of that content. Winning formula.