One percent per hour is decent, but 'idle' means different to everyone. Do you have email accounts checking every 30 minutes, how often do Facebook/Twitter/other social media apps update, etc.
Also, did you give the new ROM a few battery cycles to settle down? I noticed that I didn't get the 'true' battery length on my HTC One until more than a month after flashing a new ROM. In fact, after more than two months after flashing I could still see an improvement in battery performance. However, to be able to do a quick review, at least give it a five full (100%-20% at least) cycles to judge battery performance after you flashed the ROM.
I usually lose 5-7 hours over night on my One, but if I really wanted to save I could turn off wi-fi and mobile data (essentially airplane mode with phone radio on) before I go to sleep and I'd only lose 1-2% in 6-7 hours.