So, as the story goes there was this Master Plan of the Three Prime Evil using the soulstones to conquere the world.

Too bad there wasn't any need for a Master Plan.

Too bad the Soulstones were useless to start with, thus pointless.

Too bad the damage on one of the Soulstones never had nay effect.

Too bad no part of this Master Plan was needed the first place.

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Imagine no Soulstone get damaged. So what? Nothing changes.

Imagine the Three comes to Sanctuary the usualy way, like Asmodean and Belial, who just got there. Ye, the entire part with the Soulstones were pointless, the only thing it achieved was inactivity on the part of Hell.
The so called Genious Three were incompetent fools.

The shattering of the Worldstone - again no point. The thing had no purpose to start with. The whole "Plan Through Eons" was nothing but a low chance gamble on gaining enough time to corrupt the Worldstone, or bust.

Tyrael doing anything in the story? Nothing. He's a pathetic failure too.
MAYBE. if we assume the best, Tyrael tricked the Seven Evil on the whole BS happened in D1-2-3, just to conquere the Heavens, and with the Seven being captured under his command be the mightiest a****** in the multiverse - but then Reaper of Souls happened, and all turned out to be for naught.

Malphael is a useless cretin too. He made sure the Black Soulstone will be delivered to him - despite his own will! How moronic you have to be for this?

All in all Reaper of Souls pushed everythinig back to the starting point.castrating the lore for good.