R* really need to address the issue with graphics cards that have >2GB of VRAM.
They have been aware of this issue for sometime and a workaround is posted here:
A number of graphics cards now have >2GB of VRAM, off the top of my head I can think of:
GTX 580 3GB
GTX 680 4GB
GTX 770 4GB
GTX 780 3GB
GTX Titan 6GB
Considering at the time of the games release R* were quoted as saying that the game was designed to run on future specification PC hardware, not supporting >2GB of VRAM (correctly) is a bit embarresing to be honest.