Well, the main difference here is timing. By the time Titan Hard Mode became necessary to complete, folks were already overgeared for it and spamming Trial Roulette, so a newbie could expect a quick and easy Duty Finder win.
In the case of Steps of Faith, though, it honestly comes down to money, money, money. SE WANTS people to be able to access Heavensward when it comes out. If a player is stuck on SoF, what incentive do they have to buy the expansion, let alone to pre-order it? Early access doesn't do much for you if you can't actually access anything.
From what I've read, a MUCH higher than expected percentage of the playerbase was unable to progress past Steps of Faith. While only speculating, I suspect this may have put a scary dent in the projected estimate of Heavensward sales, and SE cracked down hard to address the issue.
It's a shame, as it's a pretty epic fight. Before the nerf, Vishap comes across as pretty much unstoppable, with the tiny chip damage your weapons do to him - cannons, explosive barrels, Dragonkillers, all these were necessary to stop the unstoppable. It was a great concluding battle to the storyline. With the nerf, a lot of that majesty is lost, but it makes sense from an economic perspective. Money from bad players (or players unlucky enough to always be matched with bad players) is as green as money from anyone else!