Heh. Well, DD and Bullseye would no doubt face off, and we know how that one always plays out eventually.
Next, I see Batgirl vs. Deathstroke happening. Cass can dodge Deathstroke, and Deathstroke can dodge Cass. That fight could go on for a very, very long time with not much progress ... if comic showings to date give any indication.
Nightwing and Deadpool? Well ... again, I see this lasting for a while with no clear winner (though Deadpool obviously has a huge durability edge).
Batgirl vs. Bullseye - it's basically the same as Bullseye fighting DD, with the same likely outcome
Batgirl vs. Deadpool - she probably can't kill him (she wouldn't try to anyway!), but she can and will knock him out
DD vs. Deathstroke - again, this looks a lot like Batgirl vs. Deathstroke
DD vs. Deadpool - this looks a lot like Batgirl vs. Deadpool
Nightwing vs. Bullseye - hmmm ... well, Dick's acrobatics might be enough to JUST dodge Bullseye ... maybe
Nightwing vs. Deathstroke - Dick's screwed, but then Deadpool and Bullseye both find themselves in equally unwinnable fights, which still results in Deathstroke facing both Batgirl and DD in the end.
Essentially, I see both Deadpool and Bullseye as weak links in this setup on the villian side, while I think only Nightwing is a weak link on the other. Therefore, the heroic side has the overall advantage.
Granted, NONE of the characters are weak ... I mean "relatively" weak.