From what I've tested, the combos off the kick don't work, as that breaks the nullify air control property of the bubbles, and the enemy can consequently AC every bubble thereafter.
The ones on Vader, Zas, Rock, (ones that don't use the kick), are guaranteed completely. Which also means that they work on characters of the same size. Example, the Zas combo is also the one you would use on Nightmare.
But here in lies the problem.. They have to be PERFECTLY centered. If the enemy is thrown slightly off axis, even from holding 3 rather than a quick 33 input, the enemy will be launched slightly angled, and one of the bubbles from the 44A+B won't hit correctly. Also, you have to be basically standing on top of the enemy when it launches. If the 33b connects anywhere near even mid range, the combo generally misses.
I played 40 matches last night against my friend who plays nightmare, and I only got the 33b to launch correctly 3 times, and only finished the combo correctly once.[I'm sure practice will help on the finishing, but its a project getting a clean 33b while standing in their face without going around something first].
I personally think this is a little much though, regardless of the situationality? (I made up a word :P), but due to the circumstances needed for these to hit (again, i reiterate, the ones where he kicks them into the second bubble DO NOT WORK), that this should be allowed.