Who said Colossus of Akros is unplayable? An indestructble 20/20 trampler as early as turn 5 sounds pretty playable to me! :D
My quickest so far, is having the colossus out and on the field by turn 4, (monstrous by turn 5) although I know that this can be achieved a turn faster with Nykthos and the like.
However, this is a deck made of physical cards, so theoretical doesn't help me unfortunately. Ideally I'd replace the two Burnisheds with two Garruk's to draw creatures to throw down.
Colossus of Akros: The main wincon. Once he's down, he's hard to deal with, especially if he's down early. Just block, monstrous and swing.
Guardian of the Ages
: good for putting people off wanting to attack, especially when they have fliers/unblockables. As soon as they do attack, he wakes up and swings for that 7 trample.
Mistcutter Hydra: Anti-blue but also because they can be played at any stage. Throw them down turn2 as fast nippers or draw them lategame and bring them down as utter monsters.
Polukranos, World Eater: A cheap drop ready to just block and defend your managens and is more than capable of sniping off key creatures with the high mana access.
Arbor Colossus: Another fairly cheap drop just to throw down if the draws aren't going your way, and is also capable of blocking those fliers, since there's few other answers to them. Monstrous on curve, too~
Karametra's Acolyte: Who actually needs lands? 21+ mana between a few Acolyte's when you have zero lands...all that needs to be said !