You can try this method ... It worked for me... Just need to buy a 64gb flash drive (32gb will be sufficient for now but since its relatively cheap and have extra storage for future expansion or updates)

I had alot of loading lag / when players join game lag etc etc... But it's all gone now...

http://us.battle.net/d3/en/forum/topic/5642269402?page=1

Hope this helps..

The link mentioned 16gb which is insufficient ... I had to buy a 2nd flash drive (64gb) because the 1st one I bought (16gb) not enough space... Atleast my post will save the OP a little bit of money lol