Malak is underestimated but I think some here also underestimate vader. Vader has a reputation of cruelty and malaise that one doesn't pick up by being a simple thug. Malak picked up the thug type. But vader... well vader had more finesse to his brutality (if you understand what I'm trying to say). Read the radio drama scene in A new hope where vader torchures leia... it's pure cruelty. imagine vader more like a rapier and malak like a broadsword. Revan would be more like a katana. Sidious was just a poisoned pin, and Dukoo would be more like a foil.
to the lighting ruling vader, put it this way. vader's grounded... yes he'd pick up the burns but his electronics would be unharmed. If you set these two against eachother I think it would be more like a protracted seige than a battle.