Add up your single target potencies. At best your 1-2-3 is 150+200+320 for a single target. 670 over 3 moves. Let’s even give that the slashing bonus and not give that bonus to death blossom spam (because most or all won’t have it up when using aoe). So that 670 with slash debuff becomes 737, or 245.6 per gcd.
So death blossom is 110 per target (not 100 as last post says) making it more damage at 3 targets (true even before the recent buff when it was 100 per). Even when it was 300 potency for 3 mobs that’s 22% more damage than a 245 potency average, and that is significant. And now with the 110 potency it’s a 34% increase vs 3 targets.
So there’s 2 threshholds, damage per gcd, and damage per tp point. Let’s say for simplicity that death blossom is double the cost (it’s slightly less). Single target you’re doing 737 potency over 3 gcd moves for 160 tp, death blossom vs 3 mobs 3 times is 990 for 300 tp. So single target is 4.6 potency per point of tp, death blossom is 3.3. So less potency per tp point, basically meaning less efficient tp wise. At 5 mobs though that’s now 5.5 potency per point of tp. So at 5+ mobs not only would you death blossom till you ran out of tp, but you’d do the most damage by waiting for tp to death blossom more, rather than going back to single target when low on tp. Even at 4 mobs considering you may be in situations where slashing debuff isn’t up the whole time, or if a mob turns/gets turned and you lose aeolian bonus (and the dps loss reapplying DE), death blossom wins.
And anytime you’re in a situation where you will not run dry on tp too soon then tp cost is irrelevant. This is the case in dungeon runs most of the time.
A9S you can get strapped for tp if you need to carry others’ dps but you should generally get an idea of how much you need to do. You need to have tp after the adds and the dps check overall is pretty low this tier, shouldn’t need to maximize that phase at the cost of running dry.