The R2 series is extremely good and can handle just about any situation, but they aren't the final word in low-light performance, either. A few other scopes have slightly better glass, and others have superior illumination. I ran a 2-12x50 for a long while and loved its optical performance. Even in diffused or partial moonlight, you could see well enough to make a shot.
Now if Meopta would just tone down the illumination to the level that the entry-level MeoSport 3-15x50 has, the R2 scopes would be even better in the worst of lighting. To account for the intensity of the illumination in the R2s, I found I have to use either the BDC-2 or BDC-3 reticle, which features a smaller dot than the 4-C. The size of the dot in the 4-C, coupled with the intensity of the illumination, tends to negatively affect one's vision in the lowest of light -- especially so when the ranges are somewhat extended.
Another thing that could benefit the scope you mention -- the 2.5-15x56 -- would be the addition of parallax correction. Why they chose to build it without SF or PA is beyond me.
One more thing about the R2: You ALWAYS need to have a watch on when hunting deer. They'll get you to and through legal shooting light with ease and can get you in trouble if you're not careful.