Well I'm frustrated... STILL sitting on 5 primordials after 2 more mega-refills after 500 runs.. so I'm now at around 600-620 runs... WTF? at least drop 1 every 100 runs above 500 devs.
That is actually a quite good drop rate! I am far beyond the 500 runs and have 3 Primordials. In the dungeon before the last one it took me about 1500 runs for 1 complete set.