T4 is entirely too easy. Endgame content has to be balanced closer together so that one activity doesn’t feel like the only relevent endgame (pits). Uber bosses should never be 1 shot.
Things that would have kept me playing longer:
Add the ability back to craft your nmd sigil level. This time it scales to pit 100/125 or where ever the general pit level is aimed for a balance point. Or heck, just let you create sigils equal to max pit level in game.
Same with infernal hordes it needs to go higher.
If you’re gonna copy raid ideas from wow, and since t4 is easy, then add mythic dark citadel. As much as some don’t want to group, I think dark citadel is a good addition to the game. I’d like to see another raid that rewards good cosmetics.
D3 had a good thing going with Altar of Rites. Some kind of progression tree that is part of an activity. For instance if Undercity was much more difficult but had an altar of rites type progression to help players through it. A progression system of sorts gives you choice and deterministic outcomes that don’t solely rely on rng. When you only have rng, then people who don’t like rng want so much loot to the point that rng is not a factor.
The big thing is probably leaderboards. Have leaderboards for pits, have a separate leaderboard for every possible nmd (given my idea above about crafting higher level sigils). I can click on my profile and it lists all the nmd I’m listed for on the leaderboards. From there I can choose to hit up a nmd i’m not listed for, or try to improve my standing one that I am listed for.
edit: regarding leaderboards, I don’t think you could do a true “solo self found” version of the game. I think you could do a “self found” though, meaning your character isn’t eligble for trading or picking up loot that was previously looted by someone else. That would still mean carries would be in play. But at least it would be something more you could filter leaderboards on.
Create an uber boss gauntlet mode with tiers scaled much higher, more mechanics. Pass one boss to get to the next, die and whole gauntlet fails. boss 1->boss 2->boss 3->boss x. Maybe boss rotation changes per season. Why? for leaderboards and earnable cosmetics.
Bring back mindcages.
Bring back gauntlet challenge rift scaled higher.
I don’t think they should give up on pvp either. Add more cosmetics there. Create some pvp events. Power creep is getting a little out of hand, so how about twink level weekly events where no more than say level 25 can enter the pvp zones?