Would it be fair to the people who purchased the game when it was exclusive, to be forced to purchase the DLC while the other platforms got the DLC for free simply because they waited? I would say so as the players on the exclusive platform got to enjoy the game a month before everyone else did, so having to pay for DLC that was released post-launch is reasonable. There is a trade-off here: they got it early, and this means their DLC isn't 'Launch Day' DLC.
The issue isn't that DLC is bad, but it can be bad, and Rise of the Tomb Raider is a wonderful example of DLC gone bad, even though there will be plenty of Square Enix fans lining up to defend what the company has done. Since DLC first became a thing, though, players have lashed out against Launch Day DLC, and we've been afraid since the very beginning that exactly this would happen. Now that day is here: a game has launched with enough DLC to multiply its price by fifty percent. That day we feared of publishers leaving out entire game modes specifically to sell them to us on top of the main title is here; this is what's happened.
By all rights, Endurance Mode should have been included from the off because it's an actual game mode. The idea that Square Enix would publish this and intentionally leave out a working, functional, and ready mode at launch so that it could sell it to us separately is appalling.
It doesn't change anything if Endurance Mode was created and finished after the game released on Xbox. The fact is that Rise of the Tomb Raider did not launch on PC until 28th January, which is perfectly in-line with the idea of exclusivity at its heart, which in turn means that the mode was ready, available, and deliberately excluded, despite being available, so that it could be used to make more money at the expense of consumers.
There doesn't seem to be much dispute that Launch Day DLC is bad. The only real question is whether the DLC that is available with multi-platform games on the days they launch is considered Launch Day DLC. There should be no debate here, because it's a tautology. The game launched on 28th January, and the DLC was available on the very same day: that, ipso facto, makes it Launch Day DLC, because "DLC that is available upon the game's launch" is the definition of "Launch Day DLC."
An outfit or two being kept behind a paywall would certainly be one thing, but PC gamers should rightly expect these things to be included as codes with the main purchase, as well - as Bioware did with Shale in Dragon Age: Origins, and as many other examples have done. Publishers justify Launch Day DLC as a method of recuperating losses incurred by used sales (which is utter nonsense - but that's another topic entirely), but, even then, the fact that something was cut from the game (Catwoman, anyone?) and locked behind a paywall is disgusting, and an inevitable conclusion to reach.
This isn't what has happened, anyway. This DLC does not exist for the purpose of helping publishers get paid twice for one copy of a product, so that excuse holds no weight; if that was the case, the DLC would have been included when the purchase was made. Let there be no doubt: these outfits, extra content, and game mode were deliberately and intentionally withheld from consumers so that Square Enix could earn more money. It's not that the DLC exists that is the problem, it's more that there is so much of it, the price is so high for all of it, and that it's all Launch Day DLC.
At launch, the complete version of Rise of the Tomb Raider cost $90, but players have the option of paying only $60 for an incomplete version. That's the issue with Launch Day DLC: it redefines "the game" and "the complete game." At launch, the complete game cost $90, although a special exists where it can be had for $80, and that's still $30 more than any PC game has a right to cost. There is no licensing fee to Microsoft or Sony to be paid here, after all, and the entire reason that video games rose from $50 to $60 in the '90s and early '00s was to cover licensing costs to consoles; for more than a decade, PC was able to cling to its lower costs, but that is fast fading, too, for no other reason than they can charge an extra $10.