I quite like them being account bound tbh, it's one of the few things left that you can't just buy. If everyone has one they immediately won't be special any more and GM will have no choice but to nerf them. Then tada you've got one but it's no use any more.
It's purely pot luck tbh, last year and the year before that I put sickening amounts of gg in and found nothing, the year before that I got 1 outside (free, lucky me). This year I've hardly even played the event and found 2 almost straight away.
If you go with the mindset of just looking for a tiger, you're going to be disappointed. Just play and have fun and if one drops that's a nice bonus. That's the way to look at it
A quest line to earn it is an interesting idea, but it'll need to be something challenging enough that you'd need to be committed to do it, not just be something everyone can do when they have an hour spare. Otherwise refer to my comment about if they were tradeable. Everyone would have one and GM would have to nerf it. Then the whole point becomes moot