Since the release of Ultimate (i think) i have only seen a single pearl, ever, it was from some random pile of trash or something similar. I see pinks and oragnes all the time (relatively, and they are usually stuff i don't want so they get discarded easily)
And yes, stuff does get obsolete incredibly fast. Thats why i made sure i had enough keys to refill at the gold chest every time i was back in sancuary. I stopped at lvl 61 though, i do NOT want to grind for any of this crap again, and the game is fun enough as it is at 61 with plenty i still have left to do.