It's not so much I want to solo a priest instantaneously, or even beat him in the long run 1v1. It's him being able to shield up, turn around and nuke me like I'm wearing quest gear, and reflect nearly half the damage I dish out right back into my face.
( http://www.wowhead.com/spell=33202/reflective-shield )
Or a resto druid putting a full row of Rejuv/regrowth/LB up then shifting out of form to moonfire and wrath me to death, then popping barkskin and rehotting, while I can't even bandage for my measly 5.8khp because the moonfire is still ticking on me.
If they even halved the spell dmg conversion for healers it would be a drastic improvement to the situation of healers going offensive. If you spec healing, be prepared to heal. Don't complain when you sacrifice your offensive capability for that huge defensive capability. I see healers on here complaining that they are being asked to be "slaves" to the damage dealers, and yes, they are right. You chose to play a supportive role, so play it and like it, or re-roll/spec.