Banning for 'Cheating'

I don't think anyone can offer an answer to this that you could consider definitive. 

One anecdotal observation I can offer, though, is that I've found most Coliseum tiers tend to become "clearable" when you have character(s) at Level 10t+5, where t is the tier number. I struggled to clear t3 of any boss until I had one or more characters at Level 35, for instance. I got 78% with Dedra on t4, but mine is only Level 39, so you clearing t4 with a Level 45 Dedra sounds absolutely fine to me. 

I don't know for sure, but I wonder if the obviously flawed cheat autodetection has a tolerance level of +/- 2 levels around the 10t+5 I mentioned? If someone cleared t3 with no characters above Level 32, for instance, would the auto-detect be triggered? 

This doesn't answer your question, but I don't think anyone could answer it completely.