Mining have nothing to do with the btc/usd price ratio. You should always report mining only to btc.
I understand what do you mean
so we must stick in BTC for mining report, not USDif we do like that, hard to make ROI in 3 months, maybe 4-5 months still possible
That is exactly it. You always calculate in BTC (invest) to BTC (mining profit).
If you're mining (hardware or cloud) hoping USD rise, but with a risk of not making as much BTC as you put in, you're losing money plain and simple.
If you invest in USD, but are also hoping for a BTC price increase, you're better off just buying the Bitcoin outright and sitting on it.