The Legendary Task Rewards are a touch underwhelming, but I knew they weren't going to be amazing or anything. Still, it seems that if a guild is going to the point of Legendary Tasks then there should be just a little bit more. Perhaps not directly, but possibly.
Which means that I like that it's a weighted random thing. That's good. What isn't good is that the rewards for Legendary Task 1 are the same as for Legendary Task 10. In fact, they could easily be worse. And that seems really wrong.
What I'd recommend, as a slight adjustment to the existing system, is that for each Legendary Task completed, the chances of getting the rarer rewards increases just a little bit.
So if you've got a 10% chance of "140 Guild Seals" on Task 1, you've then got an 11% chance of "140 Guild Seals" on Task 2. This improvement modifier resetting each week, of course.
Just so that once Legendary Task 3 is done, there's a little bit of "I wonder what we'd get with Legendary Task 4?" afterwards. Knowing that the chances are just a little bit better for the noteworthy payoff.
It's still early days, but that's the initial impressions after completing a couple of them.