1. Uhmm if they have killed two or more of them, then no they are not overpowered. Least of all uber powered.
2. Variable fighters can fold, have damn near unlimited ammo, multi-forms oh and unlike the Vajra, do have PPB, like say the Excalibur or Sturmvogel.
3. Alto was able to blast one to smithereens and Ozamu stabbity one to death.
So in the end, I cannot say they are super overpowered or even overpowered.