2 Questions I have about Vorkath from a PVM noob

So, I managed to defeat Vorkath was pretty easy imo but two things I am still having trouble with.

1. The minion still hits me (even though I crumble it instantly). Is this because my character is still attacking Vork and has to do that process first? (I am ranging with retal off). How do I cancel my attack?

2. Acid. No matter how good I seem to walk and avoid it I always get hit once or twice. I have tile markers on and everything. When I try to practice woox walking especially I get hit when my character is turning to walk the opposite way.