What the!?
How can you lose an argument because I back someone up!?
I've tried to Subrev TTar from 25% HP and it didn't die, but it could have had Def EV's.
Focus Punch on Slaking is easily countered and predicted, because say a Normal type pokemon is battling against Slaking, obviously, Slaking won't try a Shadow Ball, because they might not switch, and so Slaking might try a Focus Punch, but then, the opponent does swap to Gar, who Mean Looks, Hypnosis, Dream Eaters or otherwise kicks FP Slaking's ****.
And thus, we come to the conclusion, that Rock Slide is better on Slaking, guru at pokemon or not, you're barracking for the wrong team my friend.