Nothing is wrong.. Nicehash is the marketplace.. get that! They need a person who will BUY your hashing power.. and if his/her highest bid is everyday lower.. you will get lower reward... easy as that...
You are not mining BTC or anyother coin on nicehash.. you are selling your hashing power to the highest bidder..
Is this why NiceHash sometimes switches to algos that are clearly not the most profitable at the moment? For example, I am doing a comparison between it and Nemosminer on MiningPoolHub with both getting a single GTX 1080 and I just caught NH switching from Equihash - which was projected to earn $4.31 per day - to Nist5 - which caused projected daily earnings to plummet to $2.10. Based on what you wrote my theory is that there wasn't enough Nist5 hashpower available to fill outstanding contracts so miners got switched to the algo even though it wasn't even close to being the most profitable.
Yeah, pretty much. Basically someone bids for a small amount of NIST5 in your case, and NHML flings a bunch of computers to NIST5 to fill the order. Problem is, if you switched, you're competing with everyone else now. The NH system gets gamed like this by buyers fairly often. That's why I was saying limiting Nemos to just Neo/Equihash (usually) so you can enjoy the extra gaps of lowered difficulty when everyone leaves temporarily, while not having to "warm up" for Neo again.