I just threw in the disc today to see if the issues had been fixed and it seems like they have been
I've not changed anything since the last time I tried, but I played for just over an hour today and got zero disconnects, no paint lag and no errors
The only thing that has changed since the last time I tried is that I've moved my Wii U further away from the router as it's upstairs now and and not in the lounge
After 2.00 I'd get kicked from about 70% of ranked matched and 100% of regular matches, but today I played 6 or 7 ranked matches fine, and even 2 regular matches without problems. The regular matches would disconnect within 30 seconds before