Best way to clear low level instances FAST

When I created my paladin I was discussing with Adresa what was the best class to clear low level instances. I said mages was better than locks, a mage can use Arcane Explosion rank1 to get the mobs together then Frost Nova, Flamestrike/Cone of Cold/Blastwave all of them, while a warlock have to use the void to group them together and use Seed of Corruption. And mages are really faster... for VC, Stockades and Gnomer... then...

How can a lvl70 get into SM Cathedral with 1/3 health and mana and finish it with full health and mana without drinking and eating and pulling mobs non-stop with at least 5 mobs hitting all the time? Well.. that's a warlock clicking just 3 buttons (tap, curse of agony and syphon life)... I know prot paladins can do that too (they can get all the instance mobs together I bet)... this is broken, why I can't do that with my holy priest? =P.

The fact is that VC mobs dies fast even with the nerfed AoE spells (they was nerfed sometime ago to reduce damage if you hit more than 10 mobs or so). That not what happens in SM. Mobs there actually hits the mage and getting hit by 15 mobs = death, and I don't have mana to kill more than that. I remember that at lvl60 it was possible to get into the Cathedral, pull Mograine and kill all the mobs together with a frost mage (I saw a video.. even though I couldn't do that). That's no longer possible.. =(