I think if they were actually just trying to kill each other, which other than Deathstroke, none of them would... but if they were. I'd probably give the edge to Captain America and Shang Chi. I think their teamwork would be way better for one. But Captain America is just too strong for Batman and too good for Deathstroke. Shang Chi can also hold his own so with Cap's direction they'd be a pretty solid duo while Batman and Deathstroke would likely be doing whatever they want and not working together, making it fairly easy to 2v1 them until they're both defeated.
good one bro. but need I remind you that deathstroke is a super soldier. But yeah...as you said, the marvels have a better teamwork