I like the idea behind the Infernape Slack Off set, I didn't even know Infernape could learn it. Infernape will scare a lot of things out when it comes in so it has ample opportunity to heal itself up just like Starmie does. All this talk of giving a free turn to the opponent is ridiculous, how is healing 50% of your HP giving a 'free' turn? A more realistic scenario would be your opponent sees Infernape at low health and thinks "the next Flare Blitz is going to kill it so I'll switch in a death fodder or a physical wall or whatever". The ability for Infernape to heal up in these situations is a game changer. The best switch-ins to Infernape like Jellicent and Tentacruel aren't very threatening and Latias always has to be wary of U-turn while Gyarados doesn't enjoy Stone Edge. If the set is known then Slack Off wouldn't be nearly as effective but as a surprise move it could easily upset an opponent's plans to wear it down when a nearly dead Infernape suddenly turns into a healthy Infernape.