Cool matchup!
Deathstroke's just got some badass power on paper that give him a good advantange and i'm a Bullseye fanboy.
Some of Bullseye's flaw's are his need for melodrama and temper which make's him do something stupid things Slade could easily let him get cocky but all the time he'd be building him up for his fall. I'm guessing Slade would be able to pre-cog and use his reflex's to dodge the majority of what Bullseye is throwing at him?
Saying that though Slade's been stumped by Nightwing and there was two bodyguard's hired by the Joker that put him down well *i think i'll go find the issue* in H2H and although i wouldn't say Bullseye is at Nightwing's H2H level he aint no chump either to be manhandling Daredevil, Electra, Deadpool, Punisher etc.
Hmmmm 6/5 with the favour going to Slade i would say at the moment until i look up further feats.