Rented his rig, everything was fairly smooth but it would go down to almost 0 hash every once in a while for between 5-15 min.

I asked him about this and only got an answer the next day once the rental was over saying that it was probably my pool and not his rig.

I did have other rigs connected to the same pools that didn't have those holes in the hashing.

I would rate 7/10