After level 85 things get repetitive rather quickly. Several suggestions I can think of to enhance it futher:

1. Option to replay campaign at higher difficulty (e.g. nightmare, hell, bloody hell, etc.) or at the same scaling of player's level. You can throw in adding modifiers to enemy to increase quality drop rate as unique items are rare to find and most aren't that great...
2. Adding slot(s) to unique equipment and improve their stats. Make unique items UNIQUE!
3. Trading post or option within the game for trading purposes among players. Buy and sell system with other players using essence or gold. This can help generate a better online comunity experience; thus, more players!
4. I want to play with other people but unable to find any. I have to manually find people on this forum to add them, but most of the time they are not on! Please think of ways to make the coop and multiplayers experience better.
5. More weapon types? Example: 1h - wand; 2h - polearms; off hand - orbs; double claws; etc
6. Megabosses that may require multiple players to defeat! These bosses make endgame bosses and final campaign bosses seem like babies. The more challenging, the better!