Deathstroke's armor is typically portrayed to just help him absorb kinetic force from physical assault, as Warden said. Because while his New earth (i.e. "old" version" ) DC version lists that promethium as a component, the more modern Prime Earth Deathstroke has armor made from Nth Metal, with is just a metal that is even more durable and stronger than titanium.<br/><br/>So I would just say his armor is very likely highly bullet resistant, and he can take a decent pounding from average to slightly-above average enemies and feel nothing. But falling long distances, or being punched by Superboy, or anything with high kinetic force will still be felt.<br/><br/>