Necros wouldn't mind having wizards step in with a mana heal. I do not believe a necro's place in a raid is just to pump mana, but to dish out dps. I dunno if on SoD they increased the mobs buff slots, but if not then doing so along with allowing necros to stack their dots(as in Nec_1 casts Dot_1, Necro_2 can still apply his own Dot_1) will allow necros to have a place in raids. This would have the effect of having to retune a lot of raid encounters. I would actually love to go on the warpath for such a thing... but it's just not that high of a priorety, not for me... and most likely not for any of the developers either.
But back tot he point. I say allow a wizard to use his mana spells on others. It's already balanced out with needing 10 minutes to cast again. I also don't think many wizards would use this in a raid situation anyways, at least on another person, seeing as they'd rather get mana for themselves to get out that last nuke or two or twenty =X