Phoenix does look interesting. Is Fortitude better than having DR? I don't know I suppose it depends on how much damage you do without the +300%. Remember you can socket a Levi still. You cant do that with a Fortitude.
It's the defence thats going to make the difference. For reference, the fomer #1 ww barb uses Duress. The guy that beat him uses Eth Duress. Dr isnt maditory.