I went with a 1/3 str/VIT build on all my tanks while leveling and never had any issues with that as far as allocating points. You can always reset your points when you hit 60 if you want to go full STR.

For leveling I'd recommend two to three str pieces and two to three fending. You can carry full sets of both jewelry to mix and match. If it seems like your health is constantly going up and down, you can put on more VIT. You don't get many good cooldowns, certainly not your full tank repertoire, before 50. But it's harder to generate aggro too, esp for PLD, and str helps with that.