The best team I fought against (actually I'm currently in battle) was Fortress Gate x 2 / Anubite Warrior x 2 (preferably with Life Drain). They last forever if you know what you're doing.
Team I'm using against it:
Banner of Song (green/yellow)
--any troop, but I'm using a fully-traited Siren to have a nice start, but will be replaced by Baby Dragon--
Explode stuff with Poison Matser to fill the other 2. Wait for Dragon Eggs to be ready to cast before casting with Black Beast to devour the first troop, so your Dragon Eggs don't take too much skull damage. Dragon Eggs might get skull-hit sometimes, but FG's attack is so low that it should heal more than lose Life by casting its spell. Also, it has low attack and won't do much damage against the FGs when the Black Beast casts. Never cast Baby Dragon's spell.
Note that no troops (except Siren, who dies fast) have overlapping colors. Also note that, if the AW don't have Life Drain, your match could end sooner. Otherwise, they'll recover Life faster than poison drains it away.