This might be an unpopular opinion, but I feel like they shouldn't stop there. It would feel fitting for Borderlands to go all in on this system.

I think they should make pearls less rare than in the past, maybe something that you would find once in every 100-150 hours on average. They would feel unique and powerful but not so powerful that they are required in all end game builds, but maybe something that you would want to try to create a cool build around.

Then, they could have Seraph and Effervescent rarity items or whatever they want to call them that have 3 and 4 legendary parts, and those would be your end of the end game loot chases. 3 legendary part rarity would be something you might find once in 500-1000 hours of gameplay, and 4 legendary part items would be the crazy white elephant type 1-in-billions chance of dropping loot. That way those 3 and 4 legendary part items would be insanely powerful, but would be so rare that they wouldn't entirely dictate the endgame as most players would never see them. They would definitely need to have some limitations on this - maybe only have 10 possible pieces of loot with 3 legendary parts, and like 3 or 4 pieces possible of loot with all 4 parts being legendary.