Yes, that is since the last update.
I haven't heared of devices going back to sleep. Usually they just refuse to go to sleep, run hot, drain the battery.
Just hung up with MS. They really want to wait until next month for the monthly update schedule to fix this. Unbelievable.
Currently the only safe way is to fully power it down. Thanks to the boot time of Win8.1 this is not too bad, however, still a huge mess.