mpanju -
The Nexus 4 battery issues also traced to the msm_hsic_host wakelocks. Last I heard they believed that it was a kernel issue at some point.
MSM is the part number prefix for the Qualcomm modem, the rest of the name for that wakelock is specifying an interface or function class most likely.
The modem chip sits between your main processor and the radio transceiver hardware.
The problem can stem from bad reception as noted in the posts above, bad control software (last year's Nexus 4 kernel), or simply a stuck bit in silicon somewhere.
Please hold down power for ten seconds until the phone recycles. Unlike a reboot, that will force all the silicon to a known state.
If the issue is a stuck bit messing up control, that would clear the problem.
Look at the Gsam graph, check the box to show your radio reception. If you're fighting a low or wildly fluctuating signal, that would be the problem.
When those are eliminated and problems from other users with the same software revision as yourself confirm the same observations, then it may be time to contact HTC.
Rooting is the same thing as getting admin access on your pc, it allows you to change system software. In this case, you could conceivably go back to your previous revision or install some fix, if it occurs before HTC does it, and assuming that's the problem.
But please try to check out the first two things mentioned above, they're the more likely suspects, and ought to be eliminated first.
