I'm gaming wow on ultra settings with ridiculous 60+ fps now in every dungeon with my late 2013 imac at max settings without noticing any fan activity on bootcamp like the previous poster. it looks better than the 5k and downsampling.
here's the summary for wow on bootcamp - I've owned both computers (imac 5k and imac 2013), so don't believe any specs or generic benchmarks.
- imac 5k m295x runs wow at 2560x1440 ultra with very loud fan, bad fps (20-30 fps), bad looking interpolation and gpu temp of 105C.
- imac late 2013 780m runs wow at 2560x1440 ultra without any fan noise and 60+ fps at ultra (!) settings with crisp graphics.
I'm aware that thermal paste application influences heat management and therefore throttling - so the above specs are my results.
as always, bootcamp is far better than mac os x gaming.
the new imac 5k is not made for gaming currently, accept it please and don't quote specs. the heat management and throttling of up to 50% makes the m295x a bad choise on apple's part, even if applied correctly it would be the better graphics card. just understand that a 30% better graphics card that is always running at 50% is never as good as one that always runs at 100%,
happy I returned mine to apple. I'm sure they'll come up with a solution for the imac 5k v2 next year.
until then, I see no need to own one for gaming purposes. for photographers/video editors it's the best device however.