I talked a bit about the aff set here in the official tier set feedback thread
A couple other people like rpg have also outlined the issues with the set, particularly trying to game jackpot by dropping unstable affliction to proc an extra UA in single target to benefit your burst situations.
all-in-all, affliction is in a pretty bad state both in tuning, gameplay, and viability compared to both demo and destro, as well as other ranged specs. It needs some attention thrown at it for sure.