[SixOfSpades]

The problem with a Deathbringer Backstab is that you can't control when Sarevok will use his Deathbringer. And the problem with a TimeStop->Greater Whirlwind is that by the time Sarevok gets his Fighter abilities, it'll be too late to Dual him to Mage and still get his Fighter half back while under the EXP cap. (Multiclassed F/Ms, on the other hand, can pull that move.)

I, personally, am in favor of Dualing. He can get damned high as a Thief of Mage if you do it right away, so it's just like having a pure Thief with a great THAC0 and hp, not to mention 5 stars in Carsomyr. Or, a pure Mage with excellent hp and Saving Throws, who can wear the Asylferund Elven Chain during his casting frenzy....or cast Stoneskin & Mirror Image, then put his Full Plate back on and start Deathbringing. But, if all you want is Greater Whirlwind and Hardiness, be my guest.