I thought it all rather had to do with the GPU than the game. My GPU is fairly modern, less than two years old. Still it is a rather average Intel HD3000
but my favourite game ever, Heroes of Might and Magic V can be resource hungry at times -GPU usage, RAM usage is really low-. I learnt how to handle that (shadow quality is the big issue for this GPU, and it has to be set as low as possible, 'cos the rest of the effects run really well without putting too much stress on the GPU) but if my GPU uses a new version of DirectX to run the game I thought that, by accessing some low level features it, it would be less demanding on my GPU.