once you get over the initial "omg it's Escalation, it's OP! Nerf plx!" you'll find there's hundreds of ways to deal with them and your opponent suddenly has to try very hard to keep the bloody things alive.
To be honest, my main problem with the Imperial Knight, is that it is a Escalation unit, that can be used without the Escalation addition to the game. In the campaign we play, I have refued to add Escalation as I think it's ridiculous. But this one is a unit that has STR D weapons and can be brought either way, as it's beyond that addition. But enough about my opinions of the unit.
So to sum it up, the main ways to go about it would be:
1) 2-3 Deamon princes and either smash or Lash it to death.
2) Blobs of Plaguebearers who would glance it to death with Touch of Rust
3) Ally in Helbrutes via CSM and bring them in a formation to melta it.
Well at least it gives me a couple of ways to handle it. The fact that the shield doesn't work in CC is a big up on my early estimations, so it does help alot.
Thanks guys, you're awesome!