According to him, instead of being a full-on supervillain with powers, Deathstroke will be a hired assassin working for Onslaught. He's said to be the breakout character and his introductory scene is described as absolutely "insane." Also, Deathstroke will come face-to-face with the Suicide Squad early on and basically take down the entire team single-handedly.
Deathstroke's costume is said to be very stealth-oriented and uses an actual U.S. military tactical outfit for the basis. Like his comic-counterpart, his weapons of choice will be a sword and several automatics. The iconic orange/black mask is there, but early concept art does reveal that he will have two eyes, at least initially.
As for casting, since the role is expected to be the breakout character, the studio has been particularly choosy. Following up on last night's vague casting details, Mayimbe adds a little more: Jason Clarke is out as he has a scheduling conflict and Joel Kinnaman initially tested for the role, but landed Rick Flagg instead. Until very recently, Joe Manganiello also had a scheduling conflict, but according to the report, he may have just dropped out of Scream Queens, freeing him up for Suicide Squad. Official casting news should be imminent, but as of right now, it seems like Deathstroke is Manganiello's role to lose.