Ya they are good for other items as well that you will use more at higher ranks. I have over 4600 darks as of now and they grow fast for me. Just keep it growing and killing the NPC's and you will grow faster and faster.
Also if you really want to kill NPC's for a while and last longer there are a few things you need to work on to do so.
1. Attack
The more attack you have the more NPC's you can kill in a shorter amount of time with less energy.
2. Energy
At lower ranks you all ways seem to run out of energy supper fast and then that puts you on hold no matter what.
3. Hull
I say hull instead of defense because at lower ranks the amount of defense you get from mods is very limited where as the hull is pretty good. If you have a decent hull you can go longer without repairs. So, unless you buy Nano's and TM's, there will be less down time waiting for your timer to repair again.
Hope this helps its just a quick thing but it should help. If you have any questions about NPC fighting or anything game wise please feel free to send me a PM asking. I'm more then happy to help.
(and I'm fairly high ranking)
_________________Please check out my path guide:
http://galaxylegion.com/forum/viewtopic.php?f=3&t=30938Ship size: Colossal Galaxy Destroyer,
Because just destroying your star wasn't enough.