Can't help feeling you are being a little biased as pgrens certainly are not fine and do not keep up with baseline allied inf. Its generally accepted that pgrens are regarded as OK at best to bad.
I disagree, for what you get for the 360mp and reinforce cost Pgrens are just more useful than obers or sturms. Grens too at all stages of the game compared to volks. (talking in a 1vs1 sense here).
They trade fairly well medium range unlike shocks or sturms and if you catch a squad close range can still pick up wipes. You mention vet but apart from vet 1 their vet is pretty damn good, get vet three on a Pgren squad and there's not a whole lot of units that can stand up.