Same for me, in the same places my Xperia Z1 and LG G2 both got much better LTE reception. CM11s is more conservative in regards to bars/dbm on the status bar...which is fine. BUT the constant switching between HSPA and LTE is causing me to miss some SMS messages, and that's unacceptable. Also, crap LTE speeds on AT&T (when I can actually hold on to a LTE signal long enough).
Keep in mind, I'm in the SF Bay Area, we have LTE EVERYWHERE.
I've had my RMA open since 7/20, all they've done is email me once a day with questions regarding where I'm using it/what cases I have on the phone. No resolution.