People could fail to make a run if the RNG is against them. In Torghast you can ignore the timer element and still 5-star a run. In M+ the timer is everything if you want to improve your score. It seems likely Blizz intentionally avoided the situation where RNG is the difference between a M+ run fail or success (bad optics if ppl fail because RNG powers didn’t offer them good choices).
I don’t mind that it’s fixed but none of these power seem impactful… Volcanic Plume was best of the 3 DPS buffs on my meters and was still not in the top 10 (I could have taken no powers and likely had nearly the same overall DPS for the run). The passive ones are less obvious since they don’t show up on meters as a separate line-item; you’d have to do a near-identical pair of runs with mastery and without to see the impact.