I have not posted for a while but feel compelled to open up a discussion on this.
In the past I have read a lot of complaints about the Arcane tree being ineffecient on Mana.
Please note this is purely based on Instances damage. Not PvE or PvP.
I found that with full fire I was having a hard time against other classes such as Hunters and Warlocks on the damage meters.
Scorch is a 1.5 second cast, but I found I had little else to do on mobs but spam scorch hitting Fire Blast when the cooldown was up. This led to low damage output on trash mobs as I never really had time to cast fireball. Also the crits never really had time to tick over as the MoBs drop pretty fast.
So I changed spec and gone 40/21/0
My damage output now is sick. From the off I can cast Arcane Blast. The 40% threat reduction means I can cast straight away. As it kicks it the casts become quicker (and yes the mana more expensive).
The other night I chained 3 2500-2700 Crits (I was in the 1.5sec cast time, so about 7.5k in 4.5 secs) then dropped a PoM trinket Pryo for 5500 then a FB which didnt crit then back to Arcane Blast which crit for 3100.
The thing is becasue you can rattle so many out at 1.5 sec cast then your crit strikes occure more often.
Just to give you an idea though before you say I spend all my time on my *** drinking. My mana pool is around 9.5K buffed and I can come out of a 4-5 mob battle with about 4k left. (taking into Account that Mob's are sheeped, sapped etc). As we prepare for the next fight I just down some water as the group marks and pulls. As my sheep target comes into range I will stand up sheep then cast on the main target.
Give it a try you might be suprised.
BTW for Boss fights I use Stones, potions and evocation.
This may not work in raids, but for instances im having soooo much fun.
Anyone else using this method?