Ah, gotcha. I love TDS and will use him primarily as an exploder. I find that once he gets going, he can usually recharge his own mana with every cast. I use Sylvanimora as a back-up, but my wife uses an all-dragon team with Celestasia, Dragotaur, TDS and Emperina. In that line-up, TDS is there for AOE and to fill mana, Celestasia is there as a meat-shield, Dragotaur can buff attack and armor and Emperina can cleanse and refill life. Once TDS casts, you're doing 20 damage to everyone, filling everyone's mana and Emperina and Dragotaur can really boost Celestasia's attack so that any occasional skull matches are devastating. Multiple AOE troops aren't really needed, since TDS can cast repeatedly.
Using TDS as an AOE troop with non-dragons really diminishes its effectiveness as you're now doing 11 damage instead of 20. If you're going just for AOE, there are better options out there.