Specifically, I was thinking that he is similar to Dr. Boom in that he summons two minions to flank him when he enters into play. Two weak minions with an "effect." And his own total stats are one fewer than Boom's, while the damage output of the Treants is equal to the Boom Bots at their worst.
So why such a skew in mana cost?
These are the reasons I see:
- Cenarius is more versatile
- Cenarius is immune to BGH
- Cenarius can protect your face in an emergency
Even so, I agree, Boom gives way more value; the above reasons aren't nearly enough to outweigh Boom's sheer OP-ness. This isn't to say that I think Boom should be nerfed. He's just fine where he is imo. If anything, make him a 7/5, but not much more