Personally, I'd work on all my PvP gear for expansion if you are on a PvP server. Most of the stuff you'll be doing is outside questing. Quest after quest after quest. My guess is it'll take 8 days played to get to 80 from 70. Most of the time will be spent outside where you're vulnerable to attack by the other faction. I see a ton of high 70's still wearing their s4 PvP gear because it's so easy to get ganked while you're questing. If you get 4/5 brutal and all the guardian stuff you'll be in good shape as far as spell damage - around +1050 - more if you have enchanting for the rings. Plus you'll have resilliance so you won't get 1 shot by level 80s.