Sorry to hear about your experience. I have a wood stocked Vanguard, same caliber. I've been very happy with mine. After load development, I only shoot one load, that's the 115 gr Nos BT's over RL-22. The rifle will shoot sub-moa groups with that load if I don't let the barrel get too hot. I can shoot 3 shots at a sitting, but not 5. After the 3rd shot, the barrel is too hot to touch, and I put it in the rack to cool and shoot something else. If I don't let it cool, the groups open up dramatically.
I'm sure you already know all of this about barrel heat, so I'm not insinuating you don't. I also put a Timney trigger in mine, because the factory trigger was horrible. Nice to know if I ever have a problem with mine that Weatherby will void my warranty for that. My stock is still factory bedded though, so maybe they'll cover half?
I'm not sure how many rounds I've tried to run down the barrel between cleanings... mine's a deer rifle, not a target rifle, so the shot count is pretty low for me. I'm pretty sure I've run 25 rounds in a string between cleanings, during load development, but I doubt it's ever been more than that. And not since I settled on my load. I don't recall the groups opening up from fouling, but I do remember pulling a bunch of copper out of the bore. I just attribute that to the velocity of the bullet down the bore in this cartridge.
I guess it just goes to show that any maker can produce a turd now and again. Sorry they won't fix it for you.