Personally, I've played and liked DOTA2 but the toxic community and the fact that no one is even trying to play and come up with new ideas and just following online "meta builds" is the reason I probably won't play any MOBA games anymore since it's the same everywhere.
With the above being said, I would say Warframe > Destiny 2 simply cuz DE > Activision as devs as they have shown countless times that they truly love their game and keep surprising their players again and again with incredible new content which goes well beyond any expectations I ever had and will probably ever have for any F2P game ever 🙂
As for the Diablo... I never really saw the appeal of perpetual grind in a game that isn't really that action oriented. I mean it's isometric game, sure, it's action but isometric nonetheless. Warframe is grindy but at least the gameplay is so diverse and enjoyable that I never really minded it.
But if you like D3, I don't see what D: Immortal has to do with enjoying D3? 😃