In an ideal situation, you would dynamically recover with maximum uptime on buffs and debuffs.

The idea of maintaining a "rotation" at all is intended to reduce the complexity of handling that type of situation by providing a "pretty good" plan of attack regardless of what occurs in the fight.

The interesting thing about FF14 DRG mechanics is that all abilities are "similarish" to each other. The lowest "loose" (unchained) damage attack does 170p. The strongest attack chain averages at 253. Weakest at 217. Strongest loose GCD is 290. Every 3 seconds of clipped DOT is a mere 20 potency. That's a tenth of an attack.

Even if you clip HALF your Heavy Thrust buff, it still does 170 direct and roughly 80 bonus potency on other attacks. That's 250. That's fine. It's not perfect, but it's fine. Clipping half of your Phlebotomize (as long as the clip doesn't fail), still nets you 230. Again, it's fine.

Flubbing a positional or chain will cost you heavily though. Missing a positional sinks you down to 100 potency, instead of >200. Flubbing a chain will drop you to 100, instead of 300 or more potency. Those two errors will drop your DPS more than any optimizing or clipping or lower uptime on buffs/debuffs.

So don't sweat it, and when shit hits the fan, just Thrust.