I don't know what spec your priest is but if it's healing you need to stack spirit for regen. Wrath went on so long people forgot what it was like to need regen since you could heal or DPS and never run out of mana. My main is a resto shaman and proper healing/smart DPS/good tanks makes the amount of in combat mana regen I have work(3034 mana per 5 seconds in combat).
Focus for hunters as far as my friend says, you just have to learn how to weave your shots and rotation together.