Okay I'm going to outright say illusion slaking is a horrible set. This set is completely walled by unaware user of any kind. Most players expect this set also if they see a sheddy, belly drum and will immediately switch to their unaware to wall the living crap out of this poke. Furthermore Slaking has access to soooo many more abilities that help it much better. A few of these abilities are scrappy, mold breaker, poison heal, and contrary. Therefore there's no point of wasting a spot on a team for an inferior ability when you have access to greater abilities.