Hi Corti , we'll I'm one of those tanks that believe in a high Mitigation/Avoidance theory as imo warriors have been givven that talent and for eg. druids havn't but I'm not saying my thoery is the only right one but it's working for me . What I have noticed is that more often than not in crunch situations (whole group takes alot of damage in one go and tank goes low) my avoidance has saved raids for me then not getting hit for around 5 seconds because of a high dodge or parry stat . I allso have built up a EH set because I think at the end of the day it's horses for corses
So what I would suggest is try the avoidane thing and see how it goes for you and then decide .
As far as the shoulders go I had a look and had flashback from when I was wearing those exhact same shoulders for ages . I think the Mantle of the Abrahims that drop from netherspite is probably the easiest to come by , aswell there is a nice set that drops of heroic Sethek halls last boss .