I did utilize ohko during towely's tourney, but that has nothing to do with the subject here, other than the fact that OHKO moves are usually banned in PvP, which goes to support the concept that they should be banned from Battle Tower as well.
The team I made for battle tower is likewise irrelevant, but I will point out that I have planned for OHKO in the form of a kingdra/ shedinja which can usually kill the OHKO users. I also have Skarmory with Sturdy, however, the game is broken and Sturdy doesn't stop ohko moves from damaging skarmory as it is suppose to.
Most of that is beside the point since I am asking others for their opinions. How much time have you spent in battle tower guros?