I have Tmo and contacted support and they told me to reset the APN but that didn't help.
The only thing that looks new on my phone is a recent app called Google Connectivity Service.
Other people at work on Tmo are not experiencing this issue but they are on Kit Kat still. I don't have this issue at home, I get full LTE there.
This is still broken as of 05/20/2015 -- Possible workarounds can be found here (thanks TaintedByte).