Really shocked with your case. I have very different experiences with HTC customer support. Back when I had my HTC Sensation my display broke and my insurance payed for a HTC repair. I waited 3 weeks to get a half broken phone back. The glas had a huge gap on the bottom there was too much glue attached and the button backlight was half broken. I sent it back complaining about the repair quality and got my phone back in good condition with fully working backlight and perfectly fitting glas after 7 days. Still about 4 weeks of repair.
Another time I had problems with the paint job of the HTC One S. It was a manufacturing issue which is known with the One S. I sent it to HTC and after only 3 days I got my phone back with a new unibody. I couldn't find any issues.
So very mixed experience for me but I never experienced something like you have. It's insane!
I think HTC shoul've just sent a new device after the 2nd or 3rd failed repair. It probably would be cheaper for them.
Send from my flying Galaxy S4
Samsung Galaxy S4 16GB (my new baby as an exchange for the Note 2)
LG Nexus 4 16GB (also my new baby)
HTC One S C2 in black
Asus Nexus 7 32GB