Deathstroke is predictable unlike Deadpool how do you plan against someone whos unpredictable. Taskmaster whose powers include copying opponents couldn't copy Deadpool's because he's too erratic. It's one of the reasons why Batman struggles with the Joker.
hes not unpredictable, hes erratic. if he was so unpredictable, hed never get hit, and we all now that aint true