Even a Mk XI Borg Engine and Deflector coupled with your favorite warp core and shields is better than the MK XII Solane set for keeping shields up.
I ran that a step between stars a bunch of times and got the 4 piece solane set. It's Mk XII. I put it on a tanky odyssey and challenged a fleetmate. He shot at me for a few minutes each time. He was able to get through my shields while I only cycled 2x EPTS and 2X TSS. With a fleet shield (resb) it wasn't noticeably better, but parses showed it was slightly better. With just a Mk XI assimilated borg engine and deflector, coupled with the fleet shield (resb) and elite warp core, he couldn't break the shields. Whether my fleetmate was good or not is not the point, his reputation levels were only beginning, but the borg set was noticeably better. I didn't bother looking at the parses since the lack of hull damage said it all.
You need to look at the set's items and bonuses to determine what their purpose is. The Borg Set's stats and bonuses are clearly geared for taking sustained dmg. The Solanae Set isn't. And neither are good in taking spike dmg.
Slapping random gear and expecting to be "tanky" or whatever purpose will yield you bad results.
Pay attention to the stats and bonuses.
The Solanae Set is clearly made for offense with sci. Again, pay attention to the stats!