I don't recall anyone saying anything about decreasing the percent chance to gain legendaries from Joker boxes.
Also, everyone who seems to think there are no laws anywhere in relation to loot boxes, or "if there was a law then we wouldn't have been able to do this for the past 7+ years"...
The laws are fairly recent, and more countries are jumping on board, but they do indeed exist in various countries and some states in the US;
https://arstechnica.com/gaming/2018/04/dutch-government-rules-some-loot-boxes-count-as-illegal-gambling/
https://arstechnica.com/gaming/2018/04/video-game-loot-boxes-are-now-considered-criminal-gambling-in-belgium/
https://www.revisor.mn.gov/bills/text.php?number=HF4460&version=0&session=ls90&session_year=2018&session_number=0
https://www.polygon.com/2018/2/13/17007830/hawaii-loot-crate-laws-ea-star-wars-battlefront-2
As far as the APB economy being affected: a big part of the economy USED TO BE the trading of designs for cars, clothes, symbols, songs, etc... if anything, that market would just pick up a bit to fill the deficit left behind by the removal of legendaires from the market.
You heard it here, designers. Jack up your prices.
EDIT: My autocorrect decided that "legendaries" was actually "legionaries"... nice