Fundamental aspect(s) of an RPG are story and characters. Gameplay is a necessity, but not why people typically play RPG/JRPG.
Diablo is not an RPG. It is an Adventure game, maaaaybe an ARPG if you think such a linear and short story qualifies as role playing.
So, WRT Diablo being an adventure game I think the character progression is excellent: The more I play, the more gearI find that either makes me stronger or opens up new builds as being viable. Compared to a true RPG: There is no (progressive) story, just a back story, andthere are no important characters other than the player. It's a point-and-click loot game and it succeeds mightily at being a fun one.
I don't like how Blizzard is treating the DH. M6 or bust is current state of the class. There is no such thing as character progression in a game that does not offer endgame build diversity. If Blizz is going to be so stubborn about one item set being miles better than the rest, then it should be craftable.
I run a Mara5/RoRG and it IS immensely powerful, but it ISN'T a heart pounding dance with death kinda thing. It's great for farming parapoints and gold/shards.
So, I have all this extra DH gear, like half a tab of stuff I'd look at and go, "that's interesting,maybe later". Well, it's later. I leveled a second DH honestly to alleviate some of the clutter, and try out the other gear that's been fermenting in the cellar as it were.
And it IS a blast. I cobbled together a Shadow set with a partial Nat's set (not a fan of RoV), used my crappier RoRG and a 2 piece Aug's and a weapon that adds a rune to Strafe, and I'm off n running/dodging, ducking again. It's NOT T-6 viable, but it IS fun.
I think people really need to realize, IF you want to get to the top in an artificially created environment your options are going to be relatively restricted just like the environment.
IF you can let go of the "have to be on T6 or I'm not relevant" mentality, you CAN have fun with some of the other stuff out there.
And yes, I DO get that T6 is fun, the drops are more frequent AND the gold is AWESOME. So get yourself "something" T6 viable, and then go play with the rest of the toy box. There's some fun in there, just look for it.