Item drop rate and item quality

I have around 650% of drop rates on my main dps(lvl 97 by the time the game ended) but i noticed that i havent been getting really low amount of items and potions. Not too mention the quality of the drop items and been getting only one type of items from transmuting tower cards(more than 60%) I know that at a certain point the drop rates dropped, but if 650% drop rates getting close to 0 potions at waves 300++ is harsh. Is this normal? How much drop rate % do we need to be guaranteed a drop?

Wanted to say something similar the game is a lot harder than before ( not necessarily bad). I got to wave350 ( made a few mistakes) but had >1000% drop rate and black widow on the field and was still missing some items. The 2nd wedding ring was most annoying to wait for.

More info on drop rate increases can be found here: https://mazebert.com/2015/07/26/new-loot-function/ TLDR: Can't more than double base drops. Drop rate past certain point (~500%) has very small effect.

This not directly about the increase but drop rate in general. Plus this might be outdated with the rework. But still might be good to know thx.