Well I find the unlock method a bit odd, I mean apparently the HoT Raid Bosses work too as long as it's a kill after a reset i.e. one that will award LI. (Correct me if I'm wrong)
Although admittedly I don't Raid much myself as I was never interested in Legendary Armour and it's been a while since I killed a Raid Boss, but if I'm forced to do it then I will.
But I don't really understand why does it have to be unlocked though a Raid Boss kill, because the collection doesn't seem to have anything to do with Raids after the unlock.
Will the Ring require Legendary Insight to make? Personally I doubt it, if it did then it would probably already be makeable, instead of waiting for another LW4 episode.
More likely it will require a unique "gift" awarded for part 2 collection.
But why can't it be unlocked through other means, like Aurora was by bying the Sentient Seed? I understand that for Aurora we had to revisit all 6 LW3 episodes to get it and we only have 1 LW4 episode right now. So I understand it has to be something difficult, but why not just make it also an item which can be bought from different vendors? Like Raid merchant will sell it for 1 LI. But there would also be possible to buy it from Fractal merchant for Unstable Cosmic Essence and there could be also be WvW and PvP merchants that sell it.
To be blunt, isn't 100CM or capturing Stonemist Castle equally difficult as killing a Raid Boss if not more?
Personally I run fractals a lot so obviously it's about my personal convenience here, but like I said if I have to I will kill some Raid Boss.