If crota doesn't enrage after 14 smashes (R2) but does after 13 and a super his enrage is between 214,214 - 216,914 damage we'll say the point of which he enrages is after 215,000. unless he does enrage after 14 in which case it's 210,000. I still have his HP at 262,500.
So using Double Bubble Trouble you only need 4 downs with 2 swords to kill crota.
Here's me running sword as a warlock doing Double Bubble Trouble
https://www.youtube.com/watch?v=SH9z008H9Vc
we essentially do it with 2.5 swords.
I love that strategy, but I've yet to run it successfully w/ a group. Boomer Bubble Boogie works so well that usually that's what the fireteam wants to do. Bubble Trouble sure makes it easier for the swordbearer though.