Sorry mate but your arguments make no sense to me.
First I don't understand how, even with the current "crash" on the altcoin markets, your profitability can be declining rapidly. All coins have doubled/tripled (and more) in value within the last few months. Even if you mine less coins, the profits are still huge compared to last year. So unless you pay 1$/kWh...or I'm missing something.
You're missing the fact that difficulty is skyrocketing because everyone, their mothers, their grandmothers, and their dogs and cats are jumping into the gold rush. Take a look at any of the profitable coins' hashrate and difficulty charts for the last couple of months. They go from a gentle upward slope into an abrupt near vertical climb. So as more people/hashrate come into play, everyone's respective piece of the pie shrinks unless coin prices keep rising at an equal or greater rate.