Your Butcher's Block applies a damage taken debuff on the person you're attacking for everyone. You should apply that on the focused target to help melt that person down. Put the pressure on with your Fell Cleaves and stuns.

You'll want to use Holmgang in different ways. Keeping a target in place is helpful, but you can also use it to remove someone from the fight. If you are putting pressure on the healer, you can position yourself so that you pull the healer behind a wall and prevent them from healing their party for a few seconds, then follow it up with an Onslaught stun.

You you reach 4 stacks you'll want to prepare to go into Defiance, and use Inner Release for either Fell Cleaves or to stay alive with Inner Beast.