We are currently working on Kael'Thas to get attuned for Hyjal and up till now a (more or less) full fire spec has proven favorable. I have for the longest time been testing combinations of arcane specs including full arcane at Dr. Boom in Netherstorm but eventhough it has proven to be a superior DPS at least from spamming Arcane Blast I wouldn't be able to use it in 25man raiding for a number of reasons which I am sure most are well acquinted with.
I was puzzled to see the setbonuses on the Tirisfal raiment (Tier 5) as they seem to shine only with an arcane build. Obviously the small 5/10man instances are suitable for spamming Arcane Blast and achieving a higher DPS than fire would allow but I find it hard to believe they would place this on a raiding set if the only other bonus wasn't somehow meant to support 25man raiding. The second set bonus does seem to be sublime for Arcane Missiles and the high amounts of spi/int and crit (rather than hit which was on the Tier 4) should all add to sustaining DPM. The Tirisfal raiment looks like a set made for Arcane mages.
My question is simply this: "Has anyone with at least 4 pieces of Tier 5 attempted a full arcane build vs. a full fire in Hyjal and BT, and is arcane viable at all for raiding past TK/SSC?". Having used Arcane Blast a lot I know it isn't viable in raids due to mana consumption but how about AM?