First, I haven't had the problem, but I haven't shifted 1-2 above about 7K--only 1,700 miles on the car and haven't redlined it yet.
It is clear to me from the feel of the 6MT, that the 1-2 shift--particularly at higher RPMs--must be more deliberate than other shifts. I use my fingertips, and I never push if the tranny resists. I put enough pressure on the shifter so that it goes when it's ready, and it's never resulted in a delayed shift--one where I lose momentum and/or have to worry about the rev match.
(It has occurred to me that the 1-2 shift is probably the main source of delay in 0-60 times relative to the DCT.)
Having read this thread, my guess is that the 2nd gear synchro simply doesn't work as fast/well as most here would like it to.
As someone mentioned, the 1-2 shift at high revs is the most difficult sychronization that the tranny has to perform. My bet is that the "notchiness" associated with the 1-2 shift is there to protect against shifting before the syncho can work, and that those who have experienced the grind simply forced through the resistance. I also suspect that multiple grinds have probably damaged some of your transmissions, making the problem worse and requiring service.
Just my 2 cents.
I'm going to knock on wood now, or mine probably won't even go into gear next time I start her up.