Arcane Blast and Tier Set bonusFollow

I'm sure a lot of you noticed this earlier, but I was on the PTR late last night and noticed that my T5 Set bonus is now 5%dmg boost to Arcane and 5% more mana. That along with the 200% mana cost for casting AB multiple times means I will definitely be switching to Frost 70-74 then Frostfire at 75. I'm not sure what they are thinking. Blizz has stated that they want all three trees to be viable as a raiding specs, but right now I don't see the Arcane tree as being viable as more than a support tree. The 20% dmg boost is the only reason the mages in my guild spec'd into it. We run with a shadow priest and shaman in our group for the mana support. Are any of you going to be using the Arcane tree as a leveling and raiding spec? I think Blizz really wants us to be elementalist.

Anobix, what spec are you going 70-74? Arcane missiles cost 41% of base mana. Frostbolt is 18%. Arcane seems to be a mana hog. Frost has the elemental to give me back some mana and with the Glyph of water elemental I get to use the Elemental a lot. I do love Arcane Barrage. Fire seems cool as well. Using the Glyph of fireball to increase crit and combining that with hotstreak should fire fantastic. Threat may be an issue though.