6.4 in general was harder than 6.3 but easier in comparison to 6.1 and 6.2
Grandmaster was very fun when you get the hang of him, still costed quite a bit to get used to
Dr Doom MVP for the last quest

Duped Thing from the Nexus; duped Sym Supreme, Vulture and Groot from basic 5* and got 6* Omega and Morningstar
You win some you lose some I guess