Not much if any at all. My Sin Tank sits at
65 Shield Chance w/ dark ward
and 29.** Defense
As a sin tank your rotation is pretty much shock, wither, discharge,auto attack(or trash is you have more than 70 force) shock, force lighting.. over and over again only 1 of your attacks(2 if you use trash, 3 is assassinate) use accuracy. Your safe dumping just about all of it.
Just slight note, you should be using thrash more than that, to proc energize or gt shock off cd.
Basic rotation is : shock->wither->discharge->thrash up to x2->shock->FL
Even if you have to fill in a saber strike after proccing energize, you'll still gain dps and proc your melee crit bonus if specced 31/0/10.
Sin doesn't suffer from degenerating ressource generation.
As far as accuracy goes, looking at previous rotation, accuracy is not worth it. I'm still using level 49 mods of shield/absorb on my rakata/BH geared tank-sin in the rakata pieces since the stats on them is endurance and accuracy first. BH mods are fixing that slowly tough.
Also why did someone put strenght in the stats priority list? Even placed at "low" or even the bottom of it, it means using a mod or armoring for warrior, and it should NEVER happens.