In my experience, Moody is fairly rare in Singles GBU. This may be due to the fact that people don't have the time to stall in every match, item clause, or the possibility of an unspoken rule not to use it by some people.
Moody is still incredibly deadly, but with item clause and 3 Pokeslots to choose from, it is not as powerful as it is when it terrorized Smogon's metas. I've had one terrible experience of an octillery setting up on my Ferrothorn, though I've seen then been able to deal with it by getting Sandstorm out there ASAP so it can't just throw Substitutes freely. I've seen a Substitute/Protect/Dive/Return Bibarel but despite all that stalling it struggled to break through Ferrothorn's Iron Barbs + Sandstorm damage. Nevertheless, it's still very dangerous and may come to haunt you if you lack some way to take it out fast.