Honestly The Tribunal isn't efficient at all. All people do on there anyways is punish without looking at anything. :P I believe it is very likely you have been banned for no reason. But I find it very likely you have been banned for a good reason. Most of the people on League report others for doing bad in one game. I have seen some pretty terrible people though, not by performance, but by how their attitude is and by how they act.

I wouldn't be too happy either if my acc got permabanned, I've spent over $400.