I have a 16 shaman and 24 druid, and the difference in DoTs is tremendous.
For the druid with mantle of winter and season winter:
Frostbite - 11 mana, 24dmg/tick, duration 1 min - 21.8 dmg/mana
Swarm of Gnats - 12 mana, 24dmg/mana, duration 1 min - 20 dmg/mana
Shaman DoTs:
Greater Ghostly Blight - 70 mana, 27dmg/tick (24 upfront), duration 30 secs - 2.3 dmg/mana
Sickness - 105 mana, 35dmg/tick, duration 1 min - 3.3 dmg/mana
These examples aren't 100% apples to apples because the classes don't get new dots at the exact same spell level, but we are talking an order of magnitude difference in damage per mana spent. Is this really intended? I haven't kept my ear to ground as much lately, so if this has been acknowledged elsewhere, just disregard.