I'm in an assault cruisier too, I have the same 2 +6 to energy shield generation, in attack mode, I have the same 81 on shield energy... but that borg cube with his shield neutralizer has take down the shield... maybe, the problem was the different level (+1)... to be fair, I will try on a borg cube with the same leven that mine.
A thing I have very clear, to have any chance, to have shield, is very necesary focus all energy in a single shield.
Just I try it, I will say it.
Well... There MIGHT be a difference, but not between our cruisers.
I am playing on Elite difficulty.
This equals more energy dagage and therefore equals more shield regen with RSP.
My cubes are + 1/ +2 too btw.
But to be fair too: As soon as the RSP's duration is over the same problem will arise when the cube uses his neutralizer.
But they are usally down quickly.