Notice the ambiguity.If we ask ourselves point blank, whether Paul, as we know his mind from his epistles, would express his sense of Christ's greatness by calling Him God blessed forever, it seems to me almost impossible to answer in the affirmative. Such an assertion is not on the same plane with the conception of Christ which meets us everywhere in the Apostle's writings ;
If we call Christ “God blessed forever” it is akin to the doxologies to Christ mentioned by Meyer (who got tripped up by thinking of books as non-authentic and/or non-Pauline.). There is really nothing unusual.
Robertson-Nicoll is not writing about Christ who has these two separate attributes: