I really do not know how any cryptocurrency miners make positive roi. Every time I try looking to purchase a miner I realize that a) there are to many unknowns and b) it seems more profitable just to by and hold the coin rather than try and mine it.
Even the CPU and GPU based coins you need to set up specialized rigs but then the cpu and gpu's will just burn out and then you can not even use them for other things like gaming. Crazy world crypto mining.