I used to underestimate Kakuzu a bit, but I had an "appreciation day" for him a while ago and now really see what he can do. I don't, however, think he's above Kisame, and Deidara ranges from below Kakuzu to above him in different circumstances (that's just Deidara for you).
In the Battledome Kakuzu only really has what he's shown, and so he has no elemental advantages over suiton that matter. He can negate Deidara's explosives, but finding out that he can is another matter and might take too long (especially as Deidara and Kisame have been given all info on their enemies). Why won't Deidara be able to attack from long range? That's his whole focus as a fighter.
This'll be an elemental game, back and forth. Kakuzu's jutsu against Kisame's massive suiton. Kakuzu's katon is pointless, and bear in mind for a second here that each 'ghost' is a heart, and has its own chakra. The fire ghost's lot of chakra is almost meaningless against Kisame, and it'll just get worse as he puts more water down on the environment. Kakuzu's strongest attack in overall attack power was katon and fūton combined, but between Kisame's suiton and Deidara's C2 dragon I don't see it overpowering. Kakuzu needs to cover two directions, and Hidan can't push forward too easily when Kisame is counter-attacking with massive waves of momentum.
This is fairly close, thanks to Hidan and Kakuzu being hard to kill, but I don't think the advantage is theirs.