To answer, yes, I have seen 2 charms at the same time on trash mobs. You have to think though, it is going to be pretty rare to find that. It does 2 checks and both have to beat the odds and check=yes at whatever percentage it is at on both of them.
It warms my heart that someone eslse understands statistics!
As Xiggie already pointed out, each drop is an independent event, but if you really want, you could find out the chance that both events will occur simultaneously (in a row) by squaring the initial probability. I don't recommend doing the calculation for LDoN charms (1/666), you might be sad. If you hit that, you should be hanging out at the craps table instead of playing EQ.
