I suppose you have to factor in favorable beginnings and the battlemaster's precision attack. Using bless is also relevant.
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I'd argue that savage attacker gets stronger when you have the great weapon fighting style allowing for rerolls of ones and twos.
And when you consider all the extra dice of damage that can be stacked, like a d4 of extra fire damage, etc.
Certainly, but favorable beginnings only applies to the first attack vs the devil guy referenced, and battlemaster's precision attack is not without cost and not unlimited. Bless was actually mentioned in the breakdown post, but regardless, you can take all of those, add in a ring besides, and you're still nowhere near the +17 you need to actually hit the claimed efficacy rates.
Savage attacker actually gets weaker with Great Weapon Fighting Style, perhaps unintuitively but it does. After all, rerolling 1s and 2s is effectively the same as rolling a die containing only 3-6, which is to say a D4+2. Less variance from the dice, less benefit from Savage Attacker. Without Great Weapon Fighting Style, the average of 2d6 from the weapon goes from 7 to 8.37, a whopping 1.37 bonus, but hey it's something. With it, your average goes from 9 to 9.89, or a bonus of .9 damage. It's better in that the setup provides more damage, sure, but it's worse in that the benefit provided by Savage Attacker is lower.
Same deal for more dice - 2d6 you went from 7 to 8.37 which is only roughly 1.4 but it's nearly a 20% bonus. On a small portion of your damage, sure, but even still, proportionally it's not terrible. 4d6 you push your average from 14 to 15.93. Numerically it's better, nearly 2 instead of almost 1.5, but proportionally it's worse, only a 13% bonus. This is again because the more dice you have, the less likely it is to have outlier behavior anyway, and thus the less benefit you get from selecting between two different rolls. 8d6 you go from 28 to 30.73, almost 3 whole more damage, but not even 10% at that point, and so on. It's really just not a good feat. It would be better if Great Weapons used D12s instead of 2D6, for the reasons outlined above.
