My own two cents: I never see anything take down the adds on the pudding boss in WP as fast as a WHM. In addition to just plain faster kills, that means less time the boss is being healed, and a safer run for everyone. Yeah, Holy is expensive. Which is why you use it intelligently for situations that call for it. For other situations, you should at least be tossing out some DoTs. One can argue it's not as much damage as the DPS, but if you have the time you might as well. If MP issues are so tight you can't even afford your DoTs, you've got bigger issues.