Well shadow priests are effective dps and mana regen but VE is not going to solo heal a tank vs. any npc that hits for a significant amount. I'd probably concede elemental shaman are fairly close to solid effectiveness at both healing/dps. Their healing effectiveness is a bit borderline without earth shield though.
There's quite a big difference between a fluid hybrid like and a modal hybrid
http://blessingofkings.blogspot.com/search?q=modal