I know the R diff isn't as beefie as the RS3 / TTRS. I can say right now, my rear haldex is doing perfectly fine at Stage II+, and if it weren't for the new 8Y.5 RS3 wait for Canada I would go Vortex Standard without batting an eye.yeah, but I need to figure out how much torque it's actually sending. There's limits to the stock clutches and blow-off valve.
the thing is though, if a majority of the power is going through the front and there is a hard limit (by the factory) to the amount of torque (not a percentage) goes to the rear, the rear LSD won't be really useful.
When I got the Haldex tune, it made a massive difference on launches, but I still find the front Wavetrac LSD has been the best thing I bought especially for coming out of a corner. Since the front will ALWAYS have more power than the rear (you will never obtain a 49/51 or greater split). I still have a hard time justifying the money on a rear LSD.