It's not overpowered. I don't recall anybody complaining about the LeIG before the Brits got added to the game. The problem is that the UKF's design - with small squads that need to be in cover to be effective and lots of static emplacements - makes them especially vulnerable to this weapon. A comparable situation would be, I dunno, the ML-20 against the OKW. It's not that the ML-20 is overpowered, it's just that it takes advantage of a fundamental weakness in the OKW's design.
Pretty much this. OKW and Ostheer are designed to fight 6 and 5 man squads. So when you add 4 man squads of course things are going to overperform.