I actually went recently, and a lot of the teams were carrying 1 or 2 members with it, double team more than minimize. it didn't surprise me much, i actually lost to someone because of that..
but yeah! most of the battles i was in my opponent had double team on one of his pokemon, so that's definitely something to watch out for. as usual it's as simple as carrying a clear smog user.
yes, it's pretty common