He beat Cosmic Hulk by absorbing its Power Cosmic -which was M.O.D.O.K.'s plan all along- and he beat Skaar by using magic. Now, this is a magic empowered Hulk, so this two venues are unlikely. This version of Hulk would torn apart Iron-Man level armors if given the opportunity.
Doom has the mobility advantage, but sadly he's outgunned here.
Yep, Doom can definitively hang there, better than Iron-Man would (imo), but he'll have a hard time to surpass the damage done by an enraged Thor -to the point of one-shotting a Worthy who tooled Rulk-.
Ovoid Mind Transfer? He's done it at least four times, in different eras..
His blasts are also pretty powerful. Put down Warlock, Magus, and even Molecule Man (Though it didn't stick, naturally)..
I also wouldn't put it past Doom to just absorb the magic that's empowering Nul.. I mean, he power jacked everyone from Beyonder to Galactus. Sure, those weren't magic, but magic can be drained too..
Ovoid mind-transfer against a Worthy is actually suicidal, not to mention iffy against Hulk's very random and nonsensical split personalities defenses. I forgot to mention regular Hulk already has enhanced magic defense.
Doom blasting abilities are great, but I don't rate them above something that Thor admitted, he couldn't put down. I mean, Thor has handled Warlock easily.
I'd like to believe Doom can device some spell on the fly to overcome Nul, but we don't know if that's easy considering how everyone is faring against the Worthy. Maybe if Dr. Strange managed to disenchant Attuma...
Also, Doom had the tech he needed and Klaw (with TaaII kind of embeded) to pull that off. Replicating a similar feat -albeit against a weaker foe-, seems unlikely for the lack of context. His excellent showing to handle Nightmare was also too complex to replicate on the fly. We'd need to see Doom pulling something like this at some point to consider it a viable tactic.