I've been playing with the guy who does this setup kinda regularly (as well as helped him make it) and have tried plenty of ways to get out, and let me tell you its kinda tricky. The real problem is that I don't believe you are actually invincible during the shield (need to confirm this), as I recall being shot by the level 3 during the shield before you are free to roll. On top of that, the iceblock assist creates physical terrain that impedes your movement if your high enough above the ground (which is why he tends to do it after a knockdown)
I'm gonna test to see if you can be shot during the shield before the roll to be certain though. If you can then that means the escape isnt a guarantee, but believe me, I want to be wrong.
Edit: OK, just finished testing it out, using bugs assist instead to make things much easier for myself. You can be shot during the shield but before the roll. It actually ends up being a LOT of time before the roll comes out because of the slow down taking timing out of the equation.
What I've ended up doing in our matches have been 1 of 3 options, most of them being kinda dicey:
1) Purposely stand block Dragon assist and attempt to guard cancel (6E while blocking) just before the Ein shoots
2) Burst right before Ein shoots
3) If your far away enough from Dragon that standing wont get you hit, use level 3 or roll twice (assuming dragon wont hit you standing inbetween roll 1 and roll 2)