You might consider Mulled Tea for food. It won't give you determination, but more Piety, which can help for MP intensive fights.
Keep an Eye on your Aggro bars, and use Regen ALOT (if you can be sure, you will not draw aggro). Thats extremely MP efficient heals. Try to keep it up on at least maintank the whole time.
Use Divine seal alot, since it has a low CD.
In my opinion, theres Piety after Determination, and before Crit/SS.