I really like Fanatic of Xenagos: either way you look at it, 3 for a 3/3 trampler with haste or 3 for a 4/4 trampler ain't bad.
I don't know what your playgroup is like, but Destructive Revelry might be an effective way to offer this deck some control+burn.
I also don't really like Arbor Colossus. Sure, he's 5 for a 6/6 with reach, but he requires a GGG commitment and his Monstrous ability is pretty unhelpful. You might want to consider instead something with a little more *umph*. I'm thinking Mistcutter Hydra simply because it gives you flexibility AND he has haste (not to mention can't be countered and pro blue; not inconsequential!), or maybe Polis Crusher as he has protection from enchantments (which might be helpful in your metagame, although maybe not).
I don't know what your playgroup is like, but Destructive Revelry might be an effective way to offer this deck some control+burn.
I also don't really like Arbor Colossus. Sure, he's 5 for a 6/6 with reach, but he requires a GGG commitment and his Monstrous ability is pretty unhelpful. You might want to consider instead something with a little more *umph*. I'm thinking Mistcutter Hydra simply because it gives you flexibility AND he has haste (not to mention can't be countered and pro blue; not inconsequential!), or maybe Polis Crusher as he has protection from enchantments (which might be helpful in your metagame, although maybe not).