There was ONE time I also had 2 geodes in the pool with only one party, 3 people in party. There was wind weather present, I don't remember what day it was though. It was in Sky, I was really confused about it and I've never seen it happen again since. It is entirely possible that one of us had zoned in after the first one was in the pool and gotten the kill shot for the second one... it's been over a year since it happened but I know we were trying to pop Steam Cleaner at the time and I seem to remember zoning in after the detector had been pulled and dolls were being killed.

Whatever it is, zoning DOES help, immensely. I was farming flame geodes in Meriph (S) on firesday, and a random bout of fire weather popped. After each geode I would recall back into the zone and resume killing, and get a geode almost every single mob, if not then the second mob would drop one. I came out with 12 flame geodes on that one firesday. I've done the same thing in sky with wind weather and come out with a boat load of geodes by camping by one of the Ve'lugannon zones. I've never been able to duplicate 2 geodes/1 party, and there's been many many opportunities for it to happen. There's some kind of exception where it can happen, it's just extremely rare and I still stick by the 5 minute drop timer/zoning reset theory.