With 7.3 (and the 7's prior), my 4S battery performed similarly to the OP's. From 100% to 60% overnight while on standby. If I was using the phone (for anything--calls, texts, web, whatever), it dropped like a timer ticking down and went from 100% to dead within just a few hours. This was with suggested fixes in place, such as turning off background app refresh, location services, push notifications, dimming screen brightness, etc.
When I updated to 7.0.4, I used the process Thom_D described. That fixed some of the non-battery problems, such as random crashes, apps not running smoothly, keyboard lag, etc., and it's fixed the problem with the battery draining while in standby, but it still drains quickly while the phone is in use. It did improve a bit. Now it goes from 100% to 20% in the same amount of time, but that's still a remarkable drop from ios6 performance. Before, I could easily go two days without charging, sometimes three. A few times I forgot to shut the music off when I fell asleep and in the morning my battery was still over 80%. Now, 45 minutes of music leaves me at around 60%.
At this point, I don't know what fixes are left to try. I've already done resets, restored to factory settings, all the "battery hog" settings/features are still switched off. Until I can get a new phone, I guess I just have to wait/hope for a fix and keep a charger onhand throughout the day. Sorry I can't say something more positive, OP, but the method Thom_D described has worked for a lot of people and did fix some of my issues, so maybe it might work for you.