I'll admit, it is kind of strange, but we'd have to test it out a few more times before we can consider this a science.

I was there at croc for over 4 hours. Riley was there too (with his ALT), but they were grouped and I was solo. That means there were 3 of us. During that whole time, the ancient croc did not spawn even once. As soon as I grouped with Rraven and Mmaus, before they even got there, the croc spawns once and drops sleeves. Now Rraven gets there and the very next spawn, he was up again, and dropped the sleeves. The next spawn was the PH, but then I left and not sure exactly what happened next. All I know, before I logged out 30 minutes later, Kelrin was telling me the pants dropped.

Personally, I think it is random and this is just the luck of the draw. My reason is, I was in a group back in my 20's. The group decided to camp the croc room and someone was pulling mobs there for us. The croc didn't spawn one time. That was a full group of 6.

Like Ranis said, if this theory worked, someone would have found it by now and it would continuously be camped by groups of people.