my iPad 4 ran at a much higher temperature than my iPad 3 did plus it had really bad light bleed. i actually ended up returning the iPad 4 and going back to an iPad 3 refurb and saved $150. the real funny thing is, the iPad 3 runs cooler and has a perfect screen (no tint, no light bleed)
even though my iPad 3 runs cooler than my iPad 4, it still runs hotter than the iPad 2 i used to have before i gave it to my brother. i definitely miss the iPad 2 being lighter and how you could run that device through its paces and it will only be warm from your hands...not from the device itself. oh well, the Retina screen is worth it IMO
if the iPad 4 is running too hot for you, i would return it and buy an iPad 4 refurb. all of my refurbs have actually been of higher quality than the brand new ones (iPad 2's and iPad 3's). the refurb units get 100% inspections as they are taken apart and re-assembled and fully tested. you might not like the idea of owning a "used" product, but you get a brand new battery and exterior. you don't touch anything that was used by someone else. the only thing that gets re-used would be the mother board, the screen underneath the outer glass layer, and the interior ports and interior button switch connections. you will save $50 which you can then use to go buy a case