You are overlooking the stacking effects of Sorceress skills. ABlast and Inferno are both weak in that their damage is only applied to a monster once.
Meteor's flame damage stays around for 0.5 seconds per level of the Meteor, so the impact of a lvl 30 meteor might look nice, but the 15 seconds of flame damage is way higher. Every second you can launch another Meteor to increase the flame damage yet again. It gets pretty impressive. Blaze stacks far higher, and should be able of reaching the damage-cap every frame. Here's a
thread discussing some end-game Meteor damage as high as 400k dps.
Blizzard doesn't stack nearly as well, but it does stack about 2-3 times I think, so you can essentially double or triple its listed damage when the target is standing in the area of effect.
The Druid can not stack any of his cold spells (Arguably Tornado stacks if the Druid is under the effects of SlowMissle). Fissure and Volcano stack just as well as Blizzard, but for much less damage (no Mastery).
Summary:
If the target is still, then the stacking effects of the Sorc can be awsome. If the target is running around, and he's running along your column of ABlast, then the druid's damage will be better.
There's more to the builds than just damage though, but that's a different topic.