Its not quite there. Its quite significantly slower than the 750m and and that chip is using
DDR3-1800 mhz. The iris pro rmbp is slower than the 750m
ddr5 on the retina (I'm assuming that you mean in your macbook). The 750m in that charts is quite BW bound. Iris also performs a lot better at lower resolutions and settings.
http://www.anandtech.com/show/7238/acer-v7482pg9884-review-everything-you-need/4
Comparison to 15W intel chips is problematic because they are so thermally bound. Even with mods (4k textures and such) the HD 4000 in my laptop gets around 30-32 fps in skyrim (riverwood). (That's the only game on my notebook at the moment).
The other thing to be extremely aware of is that the AMD kaveri reference design is using much faster RAM (at least 1866 mhz and probably 2133 mhz). That is responsible for a good chunk of the performance increase due to RAM speed that OEM notebooks easily may not use.
However, if used with high speed RAM this will easily eliminate a good chunk of the low end igps. Strong performance.
I see your point but Tahiti is incredibly inefficient compared to Pitcairn. Pitcairn vs. Cape Verde is different.