If the statistics of these borg parts ive been posted around the forums are correct, then these peices will increase your preformance immensly!
So no i think them being STF rewards are fitting enough since STF's require time and effort to complete which adds well to the new borg parts since there not soposed to be extremely easy to get.
Also if you're having trouble getting a decent STF team together, join a fleet if they use TS3 or Ventrillo use that aswell co-ordernate and be organised and you'll do the STF in no problem. I cant count how many times ive sucessfully done an STF with nothing more then having a dedicated fleet who are organised and communicate well.
I have a friend who's done each of the 3 Borg STFs at least 5 times. Pick your teammates carefully and you can probably do them without too much trouble too. Heck, join a Fleet. There's plenty of them around that do them every couple of days.