+1 Monster on Cleansed map TOO Rare

I've spent about 30-40 minutes looking through many of my corruption cleared areas to see how many of these modifiers I could find. Surprisingly I am coming up with very few, around ~3-5%. This seems VERY low considering it is necessary for completing the Boss atlas. It would be great if this could be bumped up even a little to keep the player from having to go to travel great lengths on the map similar to when there were no citadel beam identifiers.

This is seemingly far too difficult for what it should be. The planning to complete as few maps in a corrupted area as possible, the RNG for even getting a +1 modifier after clearing the corruption, then the RNG for getting a boss on that same map, and the RNG for getting irradiated on the same map. I like and understand the grind, but this seems a little bit too much RNG. I have completed hundreds of maps trying to get just one of these combos.