Max life is only really useful up to level 10 or 15. After that you become a burden on the group if you have way more life than everyone else does

so I'd go for stats (str/dex) on your gear instead of max life at higher levels.
And basically just arena when you can't find a good cata group but hop in cata when you can

is probably the easiest. I prefer arena myself but basically it's just that arena is single player and cata is multiplayer
