I can see boss hp like HH but I can't see Snowman hp or regular mob hp. I checked the game settings and they are good too. Had this problem for a while.
happened to me that what solved for me http://www.thewindowsclub.com/force-full-shutdown-fully-reinitialize-windows-8
It happened to me for a few days. Now it's just randomly back. I couldn't see the monsters names under them or anything. Started working again last night.