Do you know how many copies Witcher 3 sold in 2017, two years after the game releases? 8 million copies, sold even more than 2016, half of them is on the PC. Diablo 3, which was relased back in 2012, offically released in China in 2015, sold more than 1 million copies in the first week, just in China and pc alone.
Meanwahile, it took 3 years for PoE 1 to get 1 million copies sold, on all platforms. D:OS 2 is a juggernaut in the CRPG era, it sold way more comparing to any other CRPG, no others even come close to it, yet it still take them more than two months to reach the 1 million copies mark.
1 million copies might be big numbers for CRPGs, but it means jack shit for AAA titles. Comparing Deadfire to any AAA titles that releases in this generation is meanless.
We are not talking about sales figures. We are talking about revenue generated. This is important, because you are right that The Witcher 3 sold more copies on PC in 2017 than it did in 2016, but I am willing to go out on a limb here and say that it was doing so at a reduced price. The Witcher 3 is currently 50% off on Steam, and it has regularly gone on sale with a similarly discounted price over the last couple of years. I doubt it did so only a year after release, however, given its generally strong sales. Obviously you can guess where I'm going here, since one would hope that the vast majority of sales for Deadfire in its first year on the market would be at full price, or only at a minor discount.
You're right, the original Pillars of Eternity did take more than a few months to reach the 1million mark. However, by October of 2015 it had sold 500,000 copies as was announced by Paradox. From March to October is a period of seven months. In this same seven month period, Deadfire has managed to sell just over half of what the original game did. Regardless of this, one would expect that if the original game had been something which people were clamouring for more of, that a large portion of the current consumer base would have purchased the sequel. Instead, it took seven months for a quarter of that consumer base to get around to it. We are not just comparing Deadfire to the revenue generated by AAA games, here. We are looking at Deadfire in comparison to its more popular contemporaries (such as D:OS 2 and even KCD) which
have managed to generate similar amounts of revenue in 2018, compared to one or two year old AAA games such as The Witcher 3, Fallout 4, Assassin's Creed Origins, Total Warhammer 2, Ghost Recon: Wildlands, Shadow of the Tomb Raider, Middle Earth: Shadow of War (flop lol), Call of Duty WW2 and Final Fantasy XV.