I don't know if a stam set is the best possible choice for a priest, but your set looks very nice. All I can notice is dual gnomeregan stam rings (edit: which I noticed after posting this that you already mentioned ), you'll lose 8 spirit but gain 8 of arcane and nature resist in trade. They would increase your tankiness against a lot of classes instead of minor mana regen, which would fit this set better IMO. Herbalism might be nice instead of alchemy aswell, it is a nice and powerful cooldown in a lot of different situations, and can be used both offensively and defensively.
A good stamina set doesn't only focus on pure stamina. You are gimping youself to much from good priest stats. I'd say you have to find a good mix of stamina and intel/sp to get a descent stamina set instead of having a little hp increase. You know, spellpower is life. But hey that is me.