1.
Maps with holes everywhere, turn the game into a lame pushing contest. I don't care if I get hit a few times because eventually my opponent will mess up and fall to his death. Even better is guard breaking people fighting in groups. The current mechanic of guard break disrupts good fights and environmental deaths in the volume happening in this game is just stupid and boring.
Easy fix: Put up some damn barriers and limit environmental damage so it doesn't dominate combat.

2.
Feat attacks are really disgusting in the way they ruin the combats. Just stupid. I am sure you can come up with something that actually supports gameplay instead of destroying it. Generally the feat balance is horrible.
Easy Fix: Make a playlist without feats.