The only people I can see getting any usefulness out of this are new players
And any advanced players too. And any mid-range players. Who doesn't want KP and/or spell fragments?
Those of us at the end of the tech tree have literally
nothing to do but farm KP.
The only reason I am not going for these myself is that I am going for the set buildings that will give me goods that I will use to get KP from the tournaments, and I want to help my FS to get 10 chests every week.
Getting 12 lindworms instead would get me 126 KP per week. That's like doing 25
extra provinces to 2 stars in the tournament.
Will my set get me that far? Almost certainly not, and it will be double the size of what the lindworms would take.
The only reason I'm not regretting my choice right now is the mana I will be getting from the set, which only players in chapters 9+ would care about. Players who are in chapters 3 to 8 could grab these lindworms and basically get the benefits of being in a 9 tournament chest FS every week without doing anything.
And it only produces for 100 days...before it turns into a useless culture building.
Before it turns into a culture building that gives more culture per square than any non-event/non-premium culture building.