Isn't it more difficult to get the Gotterdammerung than beating the entire game on hard? Haven't beat the game on hard or got the Gotterdammerung, but so far the hardest thing for me is to beat the pull up challenge.
I am working on this platinum right now, I just need hardened veteran and I'll be done.
Getting the gotterdammerung requires some maxed materia that you'll want for hard mode anyways (HP/MP up, elemental, etc), so getting ready for that VR battle will save you time later, assuming you haven't maxed out all the ones you need.
I'm in chapter 17 about to face swordipede so maybe I haven't reached the toughest bosses yet, but this accessory has definitely helped me a lot. Lots of encounters have been shortened by Cloud starting with an Ascension. I gave it to Tifa for the fight against those dogs that jump out of the cages (this encounter gave me hell even on normal) and the fight was over in seconds. There is a reason people recommend you get it before starting your hard playthrough.