I’ve started my 3rd alternate (4th Character). All I do is Bounties, Rifts and GRifts. I’ve had a couple of Rainbow Portals opened. One Goblin I killed opened a Portal to Not the Cow Level and one I killed opened a Portal to The Vault. I’ve lost count of how many Odious Collector’s I’ve killed.
I even tried the trick of letting my main Character run some Bounties, stashing the Cache and letting a different Character Class open them.
Still no Captain Crimson’s Trimmings Plan. 
By the way, my Demon Hunter collected and stashed the Bounty Cache. My lower-Level Barbarian opened them. The items I got were the expected items. That is, there were the Act-specific Legendary items and some Rare items. But, all of the items had Strength on them instead of Dexterity. (So, it does make a difference which Class opens the Bounty Cache).