So, we're starting to see what the colossals are capable of. On the Cryx forums, they're discussing how best to deal with the Stormwall, which is the colossal we have the most information about. Why don't we try to come up with some stuff of our own on how we're going to meet this new challenge. Since I use Blindwater, I've got a few ideas for the scaly-side.
Barnabas - a lot of the Stormwall's offensive punch is ranged based. Swamp pits cover that nicely. Also, while the thing's got decent armor, its not impervious, and its defense is pretty bad. A couple of Ironback spitters lobbing acid at it from the safety of said swamp pits will start to chip away at it. The thing also doesn't have elite level MAT, so an IF'd posse could get into it and tie it down (it'd need 10+ to hit a posse member under DoM & IF).
Calaban - Hexblast can peel off the Arcane Shield invariably cast by Jr., and Parasite drops the SW's armor down to 16, which is much more manageable. Just be sure to occult Calaban to keep him from getting carved up by the SW's guns.
Maelok - I picture Maelok having the hardest time with the SW, since he lacks the defensive tech needed to avoid getting carved up on the approach, and doesn't have the buffs/debuffs needed to actively take the thing out. My best guess is try to ignore the SW as much as possible, and instead go after the caster with a Revive/Feat assassination run.
Thrullg - Cygnar's buffs make this thing a serious pain to kill. Thrullg, if it lives long enough to get to the SW, can strip off those buffs, and make hurting the thing more likely. Colossals can't be disrupted, but taking off Arcane Shield is well worth getting the Thrullg into the mix.
Swamp Horror - Impervious flesh makes damaging the horror at range difficult without boosting, especially if you spiny growth him with a bullsnapper. He's slow, but if you can get him into the SW, a boosted bite has a decent chance to net you a critical, which can peel through boxes right quick.