Olroth's Resolve Drop Condition?

I have scoured the interwebs to find the answer: Is killing Olroth too quickly preventing him from dropping Olroth's Resolve?

I have ran over 100+ encounters with him on my wardloop and only on one occasion did he drop an OR (heavy elemental resistances + spell suppression + 90% chance to avoid all damage) and this was possible only because it took forever to kill him.

I've ran a concurrent test on another DoT char and after 15 encounters, I managed 4 OR drops.

RNG.

Also PoE's RNG is a bit dubious in places (see: tujen and rog giving many different people the same results. Occasionally you'll come across a cluster jewel or similar that has 10+ identical listings on trade). If there is any way to game it, it's deep magic.

Boss drops are very very rarely tied to kill conditions, the most prominent one being the Watcher's Eye condition for regular Elder. As far as I know there are no conditions relating to Olroth. You probably just got exceptinally unlucky.