I had to break down and erase the data from my Link amiibo. He latched on to some horrible tactics in Smash, like spamming arrows, and he couldn't handle stages with more than one platform. I took him on Big Battlefield and the poor thing just ran around aimlessly, jumping from platform to platform. He even ran passed me a few times, without trying to attack! He was at level 45, too. Oh yeah, he also couldn't cross Eldin Bridge when the gap appears. He'd just shoot off a few arrows, and then run back and forth.
The new training is going well, though. I'm focusing more on his standard and smash attacks, as well as exposing him to multi-platform stages. At the moment, he's level 17 and he's significantly better than his predecessor.
My Donkey Kong amiibo is a beast. He's level 43 and he's taught himself to follow up and combo. I'm quite happy with him.
I'll just throw this out there, but I wouldn't mind if Nintendo added FP Battles to the online modes.