Mage spec/ builds for Early/Mid game. Pvp and PvE

So, I recently got my arcane mage to 3500GS and realized I have a looong way to go to get the 700-1400 haste required. I don't know if I want to grind gear with a 2.2 sec cast AB.. boring. So my question is; what about a FFB/ TTW build lower GS? They have a bit more to manage and are more engaging. So my questions are these...

1. How much DPS am I really losing on Heroics/ PUG 10/25 mans in >4500GS? I am not in a raiding guild so I wont have the BiS anytime soon. Are we talking like 5-10% less. If so, I would trade that for more of a random/ mobile play style. I know at least TTW will be behind till I get to about 25% unbuffed crit at least. Any bad mana issues with wither TTW/FFB with that type of gear?

2. PvP has been just bad as Arcane w/o the haste. So what dual spec build for PvP? I really split my time between both PvE and PvP. I would assume that since TTW and a Frost PvP spec share gear types, that would be easier to gear than a Arcane Pve/ Frostish PvP spec. I maybe wrong.

Thanks for the help guys!