Trouble achieving 300% waystone drop chance

I have been running citadels with 4 mods for a few days to give myself margin for error. I was getting over 300% waystone drop chance every time with only 2 tablets, and this was getting me 2 fragment drops per run consistently.

However, now I am only getting around 215% drop chance using the same method, running 2 tablets with 49% waystone drop chance on each tablet, and a 4 mod tier 15 map. I haven't changed anything, and it is driving me crazy. Any advice on what I am doing wrong?