PC Gamer should do an article on the Memory leak as it might get Blizz to fix it if its being talked about, People on reddit thought it was GPU drivers but it happens with both AMD & Nvidia cards, so that is unlikely. Part of the game is asking for commitments and not giving the memory back when finished. You can run out of memory and still have ram, as it chews up Virtual memory, which is page file. It grew my page file from 5gb to 16gb yesterday. The most ram I saw in use by game was 17gb, I have 32gb so it should have had plenty to spare.