The thing is, I don't think it would have made a difference. Soran apparently gave the Twisted Sisters two gifts: the way to read the E-D shield frequency, plus some sort of an El-Aurian shield improvement. Right after our heroes figure out they should do the forced cloaking trick, the Sisters are yelling "Our shields are holding!" in what looks and sounds like utter disbelief: "For some reason, we aren't dead yet!". So Riker is firing back, despite appearances, and it's simply not working the way it should.
That's an interesting theory about the shields. I don't think I've ever really thought about it or heard anything like this before. You would think that there would have been some sort of dialogue explaining this better, although I suppose it could always have ended up on the cutting room floor.
While Generations is not a really great movie by any means, it always holds a special place in my heart just because of how I was finally able to see TNG and the E-D on the big screen. I've always wished that the battle would have been don differently. Even though it may have been an oversight of the crew to not thoroughly check Geordi's VISOR since he would have surely told them that Soren was examining it for quite a while, I still think it was an interesting idea to have them hijack the VISOR. I just wish that the Bird of Prey's attack wasn't the final reason the E-D was destroyed, even if it was done in an underhanded way.