Nah I think you're fine.
Just by how you phrased your question, you do not come across as an FOTM guy.
If you like the playstyle genuinely thats ok with me.
And I also don't think me or anyone should be the judge of your guilt, but yourself, if you know you're playing the Class with bad intent you can convince anyone, but not yourself.
Another legit reason to roll an OP class that I didn't put on the list:
- To have an OP Class as backup to use as an evening force when your faction is having a really bad day.
As I said myself I have a GF'ed 29 Enhancement Shaman that is pretty OP, so I only bring it out when Horde is getting owned by Alliance premades or just OP comps in general.