I was thinking that it would be fun if there was a kind of sandbox-survival event of some kind where you could go and have to hold out against waves of mobs. Waves keep coming indefinitely and get harder as time goes by. Maybe make it a different mode that isn’t a dungeon really, but a co-op 5 player “hold out as long as you can” type thing with different areas and environmental weapons around, maybe with multiple maps.
It is just an idea, but I feel that once you hit level 80 the only thing really to do is pvp or make a legendary. And if I go explore the whole world then it means I won’t be able to have the full experience from playing an alternate character from 1-80.