Blenderize? Untouchable? You don't have the natural attacks or base attack to blenderize anything. It's possible to get nice damage if you add incredibly front-loaded classes (Whirling Frenzy Spirit Lion Totem barbarian), but that--which is the single most powerful melee option for a treant--still doesn't take you past a solid tier 4. You'd be right up there with the other barbarian überchargers, making up for your lack of maneuvers/Dungeoncrasher/interesting abilities with brute strength.