JD isn't a battery killer at all, personally I've tweaked a custom kernel to undervolt and underclock the CPU (-100 v and max clock 800. haven't noticed a single difference in the UI but the battery is lasting (2days 7hours 24seconds - 23% remaining)
I customize JD to ping sync every 2 hours, all sync apps are also set in their own config to sync every 2 hours.
before JD and the kernel tweak I was getting around a days usage. my phone is also fully asleep the vast majority of the time that the screen is off.
JD may be overtaxing your phone, but if it's set to extreme I would think it would disable everything when the screen is off...
get better battery stats to see what's nerfing your battery, it's on the market.
Also I've disabed WCDMA in the phone's settings, GPRS is slow as all hell, but WCDMA(3G, HSDPA...) thrashes your battery, unless FD is enabled on the network which apparently helps a lot. I use wifi at home, and generally don't need the data access other than the 2 hour sync window outside of home, so this works best for me.
you have to trade off usability with battery life with a smart phone, figure out what works for you, if you really need 3G speeds all day, then your battery won't last long, if you can live without it, then my options is a pretty good compromise.