you are calculating your ROI at todays rate, Antminer d3 arrival is on Nov 2 Months is long enough to reduce your calculation by alot.
Also from research libo libong D3 models ang for release, so imagine ang spike ng difficulty on coins using x11 Algo.

Dashcoin ata ang most profitable at x11 algo, imagine in November libo libong Asics with 15GHS the difficulty jump will be really high. Siguro in a mater of days lang almost 50% will be reduced from your calculation.

Not to mention the amount of Dashcoin that will flood the market will bring the price down. To sum it up, Increase Difficulty + Price crash = Lower income,