The issue with using charges with hit taken is it's only 8% so it takes 5 times for it to proc to get to 40%, whereas powerstrike needs 4 as it charges by 10% at a time.
Another issue is that if you're hit for 0 it won't try and charge either.

I've not got that much experience with heavy weapons but i suspect retribution and power strike will both charge at a similar speed. TwoHitBack will be charging faster seeing it's a "blue" skill. so each point gives more chance of it to proc than any pink/red abilities


Not sure if you're aware but /set easy 1 will allow you to max the amount of mobs you can fight at one time to 2. This is great for your skill build.
This will not work for level 71+, Paul specifically disabled it from working at those levels.