The only delays of TA in the current tier that comes to mind for me is in P2S and P4S Phase 2.
In P2S before the limit cut happens you'll just waste TA if you use it on CD there, you just wait until the mechanic is resolved and then re-open with TA.
And in P4S Phase 2 on Act 2, I dunno if it's the norm or if TA just comes off CD there at the end of it I honestly can't remember.
But I know that I re-open again after the last tower has gone off.

I've read some people say that they don't use TA on the adds in P3S I dunno why tho, TA is off CD again when the boss becomes targetable may as well use it.