Looking just at just the PPS for two bursts of uneven length misses half the story. An example with extremes and easy numbers:
- You do 1000 dps outside your burst
- Burst A rotation does 2000 dps and lasts 20 seconds
- Burst B rotation does 1800 dps and lasts 30 seconds
- Burst A is higher dps, but is beaten out by Burst B over time
Yes, you're noting some major factors in what you cast during party buffs and weaving oGCD casts after FS. Trick and Litany are factors, but Arrow and Fey go against your argument as much as for them.
There's also the precast time of B3 making it the essentially the same as casting F1 as your opener, and the UI3 F3 leaving some room to wiggle in an oGCD with a minimal stutter (maybe none with a better ping/machine than mine).
Another factor is the fight itself; when you have to move, when the boss vanishes, and when adds appear. If you are casting B3 when adds pop or you need to phase push, that's significant. If you are at full MP casting F4 (vs low MP casting B3) when the boss jumps, that's a factor.
Sharpcast F1 is probably slightly more dps in most cases, but not always.