Yep. Melee charge +20% (multiplicative) gets you to 540. Hunter's Aura decreases your weapon resist by 27% since it looks like you're alone. that gets you to 685.8. Stacks from stuff like Beserker and point blank weren't counted in the original 450 so his base damage is actually notably higher than shown. It is then not surprising that he would hit you for 777 if you were alone and didn't have decent weapon resistance and he had his melee charge ability available.