I've might found a temporary fix / workaround. I had the exact same problem and tried multiple RUUs, ROMs and Radios in combination to try to fix the problem.
My problem was that my HTC One M7 kept restarting it self (only shortly after booting) and I also got the "Process com.htc.htcdialer isn't responding". Sometimes I got reception for a while but I lost it pretty quickly after each reboot. Sometimes it wouldn't even let me enter my SIM pin code after a reboot.
However, look at my reply in this thread (post #6): http://forum.xda-developers.com/show...php?p=53147980
I've might found a temporary workaround which works for me!