The old way to take down a PPU in NC2.1 (ie before the big balancing patch) was.
1. The APU had to cast the Holy-debuff on the PPU. (Not sure that is the right name of the weapon, and also it was a APU weapon)
2. Once the PPU was de-buffed, someone would quickly cast noob shelter and deflector. (Usually a PE or a PPU) But often a noob heal was all that was needed.
3. Everyone shoots the PPU dead.
In NC1 to 2.1 The PPU had no chance to fully re-buff himself with his own stronger holy self-buffs, since it wasn't possible to override this. You either had to escape to the underground, and get a APU on your side to de-buff you.
Also some clans out there were so good and quick at this tactic, you often didn't know it had happen until you was dead. Whether this was by genuine skill, or by hacks, I don't know.
NC 2.2 The Game has changed... (Unlike in Tron, the graphics haven't!)
1. The PPU had to cast the Holy-unprotector on the PPU.
2. Once the PPU was de-buffed, someone would quickly cast noob protector, and deflector.
3. If the PPU is awake, he will usually spot this, and re-cast his shields.
4. Everyone then tries to shoots the PPU dead.
Now what it shouldn't be possible to do is for someone to overcast their own shields over you whether strength/quality they are over your own shields, which does sound like what's happening here.
And yes, it's a shitty tactic. Isn't this a game supposed to be where you show off your l33t PvP skills, not your n00b-buffing skills?