How about his:
Remember the two variables:
Bitcoin Price and
Bitcoin Difficulty, buying a contract you counting on the bitcoin price will rise the same or more as the bitcoin mining difficulty.
This Difficulty rise can overtake the bitcoin-price growth overtime.
Is this more clear?
If you decide between mining and holding, you need to calculate in Bitcoins, not dollars. So if you invest 1 Bitcoin, days-to-ROI is when you recover this 1 Bitcoin back. The price is only relevant when you calculate maintenance costs.
I guess there is a misunderstanding here.
When bitcoin-price is growing, more people are attracted to mine bitcoin, ergo bitcoin difficulty rises.
When bitcoin-price is dropping, more people run away from mining, ergo bitcoin difficulty drops also.
So there is a correlation between bitcoin price and difficulty. In the past year both were about the same, or the bitcoin-price-growth was greater then difficulty rise. Due to the fact (as you already mentioned) that maintenance and electricity were calculated in dollars there were less bitcoins mined, but also less maintenance/electricity cost (which is a substantial part), so the netto earnings in bitcoin were about the same. That's why cloud mining was profitable in the last year.
But the situation in the years before were different so it's not possible publish this as certainty for the future; it can be a good or a bad investment.
Altcoin mining is a different story: scrypt / ethash / x11 mining difficulty is going skyhigh but prices are following slower so those cloudmining investments were very good and are at this time very very bad.
Yes, this seems totaly right to me.