Its probably bad RNG that gave you that result.
Maybe atm its best used against stationary targets like weapons teams or crippled vehicles.
No, no, no!
According to what tests I 've done, and I did enough, on my (soviet) vehicles and AI-controlled WM infantry units (and weapon teams) I 've seen that :
1) On light vehicles the damage is lot greater when the attack comes from the sides (for some reason). Hits on the front deal deal to little damage (somewhat reasonable since its frontal armor) and hits on the rear always deal less damage that side hits.
Afaik, armor values are divided to front and rear and there is no different value for side armor (side hits are calculated based on rear armor value). Isn't that so?
So, its probably how the ability works (maybe how many rounds land on the target) rather than how much damage the ability deals on rear armor.
2) On the AI-controlled(Easy difficulty) infantry the ability fails to deal significant damage on infantry squads. Even if the squad is a Gren squad not in cover with half(2/4) squad members dead already, a direct hit from this ability fails to wipe the half-dead squad and sometimes it fails to to even kill a single soldier. Same goes for weapon teams.
On my own (soviet) squads the ability deal no damage at all. What I thought is that it had friendly fire turned off. On the other hand Stuka Anti-tank Run (WM Close Air Support Doctrine), which is a similar ability, deals significant damage to infantry, even your own. I can't say why this disparity exist.
I 've spend more than an hour testing this ability on various targets and multiple times. It can't be just a matter bad luck on RNG.