Well, in HW, you had the 90s cooldown so the sync should've been somewhat natural. Never even considered it, to be honest. (I should state my bias that I was a staunch opponent of holding BfB in ARR. And to this day, I still am biased towards opportunity cost avoidance > marginal gain.) Are we now faced with an era of pooling BfB with BL?
First, I want a fuzzy estimate of Litany interpreted as a damage buff. At 20% natural rate, around 2000 crit (similar to around 1000 crit for the same in HW... it's almost like they plan this stuff!), the multiplier should be 1.55x. So, 1+0.2·0.55=1.11 naturally, and 1.1925 while under Litany. So, interpreted as an averaged-out damage buff, it's 1.1925/1.11=1.074. Pretty close to an eye-ball guess of 1+0.15·0.5=1.075, unlike HW (where at 20% rate it would be ~1.080).
(1.15·1.074·20+1.15·8·20+1.074·3·20+480)/720=1.046 synced naturally (it takes 12 minutes!)
(1.15·1.074·20+1.15·20+140)/180=1.043 manually synced
In other words, I wouldn't intentionally hold to put these together. But I also wouldn't necessarily complain if it were forced to happen... or if we had 160s Battle Litany just to make most of our teammates bemoan the timing ;D
It's not a situation I've run into before. I'll talk about something else, perhaps the reason why I can't corroborate: I've pretty much erred on the side of clipping into FT slightly when a Life Surge problem comes up! For years!
I've gotten away with it despite how counterintuitive it is; isn't clipping bad? Yes. Very. But the problem is, that doesn't hold so strictly when there is a fairly immediate interplay with your GCDs. It's better considered a part of the GCD subsystem, kinda.
? (/ (+ 180 190 230 270 290 390 150 240 440 290 390) 27.0)
113.333336 ; this might be your rotation, ish.
? (/ (+ 180 190 230 270 290 390 150 240 (* 440 1.25) 290 390) 27.25)
116.33028 ; LS with a really really bad 0.5s clip on FT but smooth for the second cycle
? (/ (+ 180 190 230 270 290 390 150 240 440 290 (* 390 1.25)) 27.0)
116.94444 ; smooth all the way through but you wait for 5th step
? (/ (+ 180 190 230 270 290 390 150 240 (* 440 1.25) 290 390) 27.1)
116.97417 ; LS with 200ms clip, which most people would notice
So uh... yeah. Maybe this is bad, but in that case, "ahm bad".