1) I think dungeons just need two difficulties, like raids and trials. I don't even think we need mythic+ or this kind of system. But at least 2 difficulties, especially if we only get one dungeon per patch.
I also think that the same should apply to 24-man raids as well.
That would give raiders a little challenge to work on during odd-numbered patches.
+ aside from the struggle of putting a team together, watching Delubrum Savage runs was fun.

2) Raids became like that because people do not like trash pulls, and that's probably also why they added some solo instances in the Omega quest for example: so you just have to do it once and be done with it.
The sense of exploration in Coils was also related to the fact that there was no 'story mode'. The story and exploration was one of the rewards for doing the raid. You will never get this back.
The problem in terms of exploration with Eden is that it did not have any of those solo instances where you'd make your way to the next area either. It was just like "Oh let's go to the thunder plains" and we then get warped to the thunder plains. "Let's go to the jails of Eulmore" and we get warped there etc. That's why it really felt like moving from one boss to the next with nothing in-between.

3) Gear gating is not fun IMO. But maybe that's just me. I think they could give more rewards for doing min iLvl/no echo runs in general though.

4) Maybe it is boring, but since we are speaking about end-game raiding, it means we are mostly speaking about people who would try using the optimal stats anyways. So everybody would use the same items in the end, no matter what.
As you mention, Bozja proves that you can have fun with things....by breaking the balance. And I don't think breaking the balance would make savage raiding better. Rather the opposite in fact...
IMO, more than the gear itself, the carrot should be the fun of figuring out the fights together with your mates. If fun is not enough to make you sub, I don't think gear progression should.

They should definitely step-up in the amount of hard content they are releasing though. Especially with the amount of WoW refugees coming in lately, who are used to playing a raid-centric game.