No class in the game doesn't change spec per fight. But if you're talking pure single target damage DP is best on paper by a good amount
Simulationcraft Results
You should learn to read the results
1st - your link assumes 695 gear,not 660... So the closest results can be seen here
Simulationcraft Results
2nd - both results assume bis gear and tier 17 set including their bonuses -> noone has currently access to them, and even when simcraft says that they deactivated the bonus, they take them still into account (load the program and choose one of the pre-made profiles... The bonuses are still in there)
3rd - results take into account all buffs,food,flask,pre-potions, all debuffs and heroism/bloodless
Knowing all this and comparing the results from both routines with simcraft should show you that they are both outperforming the simcraft results by far a big amount of dps without even half of the advantages they assume.
I can't say if the results from the routines are good or bad all in all, but I can say that your assumptions are completely wrong, cause you are looking at the wrong statistics.... Never trust statistics u haven't made in your own
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. (or faked on your own)
Simulationcraft Results are fine, but only if you are able to read them the right way...same for simming your own toon without setting up the routine and / or simcraft to match your test case and compare the results with the routine only to say the routine is under performing. Or did you ever edit your imported toon? (flask, food,pre-potions and precasts are always part of it and have to be removed for most of your test scenarios)