Correct me if I'm wrong here but isn't the official dvi specs only support 85hz at 1080p and 60hz at 1440p. And does not support 4k at all? So really I don't see how this is an issue. If you want to run faster than 85hz and be within official specification you need to use dp or hdmi anyways.
Design flaw? These speeds are not within dvi spec.
This. Those poor TMDS used to only go to 165Mhz. Then they (apparently) doubled their speed, to 330Mhz. Any more than that is overclocking the display output bus, same as overclocking PCI-E or SATA busses.
Yes, there can be workarounds, but admit it, fundamentally, this is running out of spec.