Shadowpriest Damage may still be a tiny bit too high. This is purely anecdotal, and this is probably due to alot of fights being so ideal for a DOT caster, I haven't seen a mage as #1 DPS until very recently on a Void Reaver kill. But I agree that Shadowpriests are the 'ideal' hybrid - they bring something to the raid so valuable and needed that I almost wish we had one for every group. They provide large amounts of syngergy with other DPS casters (espescially locks) and generally fit in perfectly with pretty much any raid. Warlocks provide some of this with CoE/CoS, plus Healthstones and Soulstones, along with being insane DPS. It almost seems that Mages need a boost in this department - maybe a debuff added to Arcane Blast that reduced all Magic threat caused by Damaging Spells 2/4/6%? Or some other small syngergistic boost.

-40% threat on arcane spells for 2 talent points isn't enough? With a shadow priest with enough damage in the group, the mage will be able to use arcane blast an awful lot too.

Updated my post. My spreadsheet doesn't account for lag, so 0/5 and 1/5 are significantly different dps values..

Going from 1/5 (which with lag is about the same as 0/5) to 4/5 is 1.8% or so increase.