Yeah the point on exposing rear armor is very true. I've done in more than one of those wave serpents, and then the flamers just stand there and do nothing while the guys holding them get dead.
Now on the plus side, if you're not jetting to an area that is highly populated or dangerous, and the enemy has no remaining outflankers to pop it with, then it may not be terrible. But that kinda puts the upgrade in the realm of 50/50 usefulness, you know?