I don't think that the Reman/Romulan sets are that much worse than the other endgame sets. They are just intended for very specific roles and ways to use them.
They give a speed bonus to plasma torpedoes, so they are good for torpedo ships based on plasma torpedos, such as the Romulan Hyper and the Omega (in addition to regular ones). On a torpedo ship, you run full power to shields, so the lack of any resistance bonuses on those shields does not strike as hard. The capacity of the shields is also rather high, so they can possibly survive one of those NPC one-shot crits we all find so annoying.
As I see it, the Reman set is for a defensive role, while the Romulan set has an offensive component with its bonuses, better for torpedp-boat escorts than sci ships.
The only real issue I have with these sets is that there is no equivalent to Elie STFs, rewards-wise, to get Romulan Marks, of which you need tons.