I flashed both versions of this over the past two days and didn't get a single signal drop.
Sitting at my house I can have three bars with -100db on stock, then flash an aosp ROM and show two bars with -100 to -105db.
Looking at the db will give you the best idea of signal strength. I've flashed every ROM put out stock and aosp and I have never had an issue withy signal dropping.
It might be a hardware issue with your phone.
One thing you could try (if you haven't already) is to flash a different radio. In the g2 original android thread, there is a thread with all the radios in a zip form.
Read the first few pages, he references his other thread to back up your efs data, back it up! (If it gets botched you are screwed, as each phone has its own)
Reboot into recovery and flash it.
I'm on 10b but am running the 12b radio, I've also used 11a and all have been fine.
Sent from my VS980 4G using xda app-developers app