Great post! There are indeed a lot ponzi's out there. I have been been victim of one. also it is true that most people don't take into account all the right criteria. Therefore I wrote an article about it describing all the points you mention and giving a shot at CALCULATING the estimated payout taking into consideration the increase in difficulty. I test and compare the 3 biggest cloudmining companies and try to calculate the estimated ROI and total returns in a google sheet. you can find it on: 
https://steemit.com/cloudmining/@circularitylabs/everything-you-need-to-know-about-bitcoin-cloud-mining-comparing-genesis-mining-vs-bitcoin-pool-vs-hashflare-vs-minergate