Few things:
1.) As a tank, both WAR and PLD, your main focus should be to survive. However once you reach the HP threshold for the content and have assured your survivability, DPS should be your 2nd highest priority. Whether you like it or not, your DPS contributes to the overall DPS of the group, so the key to be a good WAR/PLD is maximizing effective health to a point and then using everything else for DPSing.
2.) You gain more DPS from Crit than you do SS. You don't gain any mitigation from SS or from Crit, the only possible mitigation based secondary stats you can get are Parry (which scales like booty among a plethora of other problems) and Spell Speed (which afaik isn't available on any left side gear for PLD). Yes, the gains of any secondary stat are marginal and you can have gear with only Piety as your secondary stat and you will have only a small percent less survivability/damage over the course of the fight. This, however, goes completely against the point of your question - you could replace Crit with anything, so why does it matter that you get Crit? What would you rather have? Would you rather just have gear filled with Parry and nothing else? I'd be all for Spell Speed gear if WAR and PLD didn't share 99% of their gear, but as it stands the only things we'll get are Parry, DET and Crit. The only thing you should concentrate on is having as much of your main stats (VIT and STR) as you can get, trading VIT for STR when necessary (ie i90 crafted accessories vs i110 VIT accessories) and reach the accuracy cap for the content you are currently doing. If, one day, they make secondary stats useful then maybe you'll have some weight to your question but as of right now they could give you nothing but Crit on all your gear and it would only make the smallest of difference in your DPS, same with Parry on mitigation, etc. etc.