i also have a 5d mark iii, i never knew about this testing until i read your post. so i decided to give it a try with cap on at iso 100 30s i saw only 1 ho pixetl, iso400 30s this time i saw 8, iso 800 30s 14 hot pixels and iso 2000 at 30s around 20 hot pixels. when i turned on noise reduction for iso 800 at 30s i think i saw only 1, so if you are concerned about hot pixels, just turn on nr and you should be fine. i know your hot pixels are consistent at any given iso, i think it's normal (12), if you decided to send to canon they would probably say the same, unless you have dead pixels, than that would be different story.