Does the Martial Adept superiority dice scale up alongside the Battle Master fighter's superiority dice if you acquire the subclass after the feat?

Question

Assume two 1st level Rogues, Alice and Beatrice.

Alice gained 3 levels of Rogue and on her 4th level of Rogue, instead of an ability score increase she picked up the Martial Adept feat. She later gained 3 levels in Fighter, and chose the Battle Master archetype.

Beatrice gained 3 levels of Fighter, and chose the Battle Master archetype. She then gained 4 levels of Rogue, and instead of an ability score increase she picked up the Martial Adept feat.

Alice and Beatrice each now total four Rogue levels and three Fighter levels, obtained via different paths. Is the superiority dice gained from the Martial Adept the same dice for both Alice and Beatrice?

(The text above was posted as an example in another question that was closed as too broad. After talking to a moderator, it was decided the best thing would be to post the example as a separate question.)

The Martial Adept feat says:

[...] If you already have superiority dice, you gain one more; otherwise, you have one superiority die, which is a d6. [...]

The already have implies that you need to have superiority dice when you acquire the feat, otherwise it is a d6. Beatrice is safe. RAW, she already has superiority dice when she gets the feat.

Is Alice stuck with a d6 superiority die for the rest of her career?

Answer 1

This was errata'd in 2016 to read...

Martial Adept (p. 168). The superiority die is added to any others you have, no matter when you gain them.

It was pretty black-and-white (or black-and-yellow, in the case of our color scheme here) - the order didn't matter.

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Unfortunately, in the 2018 errata (which they stealth-swapped the file at the 2016 link), they've changed the text again. It's once again ambiguous because they removed the "no matter when you gain them" bit.

Martial Adept (p. 168). The first sentence of the second benefit has been changed to “You gain one superiority die, which is a d6 (this die is added to any superiority dice you have from another source).”

Answer 2

As of the first errata, it doesn't scale regardless of when you get it.

As you point out, in the original printing of the PHB, the second bullet point of the Martial Adept feat read (PHB, p. 168):

If you already have superiority dice, you gain one more; otherwise, you have one superiority die, which is a d6.

However, the very first errata in 2015 corrected the Martial Adept feat to read as it does now (emphasis mine):

You gain one superiority die, which is a d6 (this die is added to any superiority dice you have from another source).

However, that errata document (and every other one up through 2017 or so) incorrectly (or unclearly) summarized the change as follows:

The superiority die is added to any others you have, no matter when you gain them.

Many people (including, apparently, Mike Mearls) seem to have mistakenly understood this to mean that the Martial Adept die does scale with the Battle Master's superiority dice regardless of when they get the feat vs. the subclass. However, what the revised wording of the feat actually means is exactly the opposite - that this superiority die is separate from and in addition to any existing superiority dice. It's a flat d6, and does not scale with the Battle Master's superiority dice.

Some people (including me!) were confused when the 2018 PHB errata quoted the new text, thinking it was an abrupt new change (though it's not marked as "[NEW]" in the errata document). However, the only new thing in that regard is that the 2018 errata consistently includes direct quotes of the new/current wording, rather than paraphrasing it as previous errata PDFs did (which can potentially lead to confusion, as in this case).