Pretty much every warrior runs full Strength bonus stats all the time. They're the tank primarily brought for their damage output, and Defiance compensates for the HP pool.

Just maintain a set of both Strength and Vitality accessories and mix and match them depending on the encounter. Ideally you want to be full strength spec with 5 strength accessories all the time, but when a bit undergeared for encounters or making huge trash pulls you'll want some Vitality accs to just give some leeway to the healers. There's no real right answer as sometimes you'll want 4 Vit 1 Str, sometimes 3+2, sometimes 2+3 etc - it varies based on the encounter and your gear level and part of the skill of a warrior tank is knowing how much vit they can get away with losing in exchange for strength.

OR... if you have 3-4 million to spare, buy a set of i150 HQ Accessories max melded. Each one has 31 Str and 29 Vit on and blows away even the current i210 accessories as an all round choice on just about all content. It's a money investment but the performance difference you see with a pentameld set is really huge.