They might look overpowered, but only against ships of your level. Those sets are meant to help against the bad guys from the raidisodes. I always hated the die/zerg when playing with pickup people. I hope these sets make it a little better surving the final boss ship in terrordome.
The item sets really aren't over powered, they are just so much cooler than the generic loot you can pick up. We just need more such items with more varied ways to get them so everyone can have a chance at getting a set without having to do what they don't want to do. It would be very sad to see them Nerfed into being the same old boring items we get everywhere else.
even the 110% Defense doesn't tip the scales nearly as much as you think. It might buy you a few extra hits, but it isn't going to turn an escort into an unstoppable killing machine, or a cruiser invincible, or a science ship untouchable. It's just some cool bonuses that add much needed flavor to the ship equipment.
Really, i think the Appearance is going to get more envy than the actual abilities that they provide.