[GAMEPLAY] Vladimir's sanguine pool (W) useless against Garen's Spin to Win

Just got in a game against Garen with Vladimir. Every single time I pooled and he spun to win, I would still get all the damage from his spinning attacks. This occurred if I started the sanguine pool before as well as after his own skill. Isn't the pool supposed to render Vladimir untargetable?

I raged, but didn't quit, but Garen got fed as hell. The problem still remains whole. :)