I'm kind of the same way where 20 seconds in my DPS is way higher than where it finishes. I just assume its RNG with early crits and trink procs going off.
I was in a group with Nowak last night and he did like a 2 minute pull on the Boralus dummies and was still 700+ after 2 minutes, but after the 1st like 30 seconds he was near 800.
I havent seen the dummies in Zandalar but I will say the Boralus ones are literally right on top of each other so its impossible for a whirlwind or lifesteal to miss.
As for overall #s and why people are pulling what they are pulling I'm leaning more towards 15% haste and then crit and verse being priorities.
I know the sims dont show it but I cant argue with Nowaks results.
Also
@Zly thanks for taking the time to do this stuff, its pretty cool.