So, Deviljho is technically faster by a little bit, as he is MHS+ and Tsunade is only Massively Hypersonic, so speed edge goes to Jho. Plus, his saliva actually super corrosive in nature, meaning that it lowers the durability of foes and loosens the flesh of dead animals, so this could help in dealing damage overall to Tsunade.
And also, should Tsunade get struck with any of the Dragon Element, any Elemental based attack she has will be reduced in power.
However, Tsunade is still mroe durable and has slightly superior AP as well, meaning that so long as she can land a hit on Deviljho, she has the potential to win. Not only that, but she is most likely smarter, which would allow her to come up with some good strategies, givent that we know she won't get one-shotted.
HOWEVER, this is all ONLY possible if we assume she starts by releasing the Strength of 100 Seals. Outside of that, she'd have most every disadvantage. The moment she activates it, she has a very great chance of winning.
And, just to make it a point, I kinda feel that Katsuyu would be a tad useless, given that I doubt it could actually hit the Jho.
So, my thinking goes like this... Since tsunade doesn't START with her Strength of 100 Seal released, she'll expend some chakra and take a few hits (Assuming one of them isn't strong enough to just outright kill her), and then releases her Seal, suddenly being able to Match the Jho. Due to the low stamina of the Jho, it'd likely try to run off to devour something a little more helpless, which may grant Tsunade an opening. However, given the pain tolerance (It can keep fighting after having it's tail cut off without really caring, mind) and the still superior speed of Deviljho, coupled with the corrosive spit of the Deviljho, he'd still be landing hits and slowl witling down Tsunade's durability. Plus, Deviljho are still strong enough to take on and kill Hunters who are supposed to be highly strategic in their approach to Monster killing, so Tsunade being strategic and roughly near it's own power isn't really anything new for it, I guess. So, I side with Deviljho, Mid to High Difficulty.