Are mercenaries capable of influencing rarity of items found?

There is a single Reddit thread on this topic with a lot of opinions.

Some people point out that there are services of people hosting maps totalling 300k gold per map, but i cant find any info about it.

Someone even suggested to set up -100% or less rarity on merc and see if only blue and white items drop.

What are ur opinions and maybe evidences either proving or refuting that capability?