Yeh, there are work arounds but really there's no excuse to not have it on par with the competition after all this time.
290x has 56% higher pixel fill rate than GTX780. GTX780 has 28% higher pixel fill rate than Tahiti.
Tahiti and GTX780 both have 288GB/s memory bandwidth, 290x has 320GB/s
As resolutions increase these two factors are likely hindering performance much sooner on the 780 and allowing the gap to grow in relation to 290x, while at the same time to close in relation to 280x.
280x isn't
that close and 290x isn't
that much faster either, 780/Ti just don't come with "uber" mode out of the box lol. Raise TDP and temp limits by the same amount and similar increases are seen. That's why review sites like computerbase.de are smart enough to test 780, Ti, 970, and 980 at two separate settings - default and "max", performing the exact same function as "uber" mode.
In a
review they did about a month ago across 15 games at 1600p, 780 is 13% faster than 280x (Tahiti has done well to even get that close in 280x form given 7970's launch state) and 290x is 6% faster than 780. In "uber" mode the 290x is dead even with a default Ti, and 7% slower than the Ti when set to "max".
At 4k the "uber" 290x gains ground and is 7% faster than default Ti as expected, but 1% slower (I'd say even) than the Ti at "max".
A couple side notes too, 780 has conservative clocks with more oc headroom than Hawaii, my 780's have a ~35% oc on the reference coolers for example. Secondly, every modern review I've seen that includes a 280x is with an aftermarket design.
Make of that what you will, but it all contributes to real world user experience.