I had huge problems while trying to use "youtube builds" and some other rubbish. Afterwards I used my pretty standard burn build with a decent use of Q+E (while he is in draw stance and charges you) or just 4+2 and freeze him with 3 afterwards. If he uses his dragon stance or your iframes are on CD, you still can use frost sheath and ice block. Or a 6 sec immunity potion. And every stance change is a free window to deal some dmg to his face. Just keep hitting. He is pretty easy after a few kills. It's just timing and practicing.^^ You can do this! :)