He is very much worth it!! I know it not only because I like Jasper and the romance itself, but because although I didn't get the historian secrets this (my first) go-around for his route; I still had a happy marriage with him because I got 2/4 legendary endings.
(Though I expect if you only got the Revaire legendary ending + no worst endings for the other three, it would still be enough to get the happy marriage prompt. Since the Isle's agreement with Katyia continues because peace still exists, and even as a Historian Jasper believes in Katyia's legacy which is why he wants MC to succeed so much especially because he can't directly interfere.)
I still haven't figured out how to get the Wellin/Skalt or the Corval/Hise legendary endings though. The best (and only) ending I've got for Wellin/Skalt is the green ending (which I guess is the best ending under Legendary, but I really have to wonder what I'm missing to get the best) and for Corval/Hise the best I've managed to get is the blue ending lol (and again, no idea what I'm missing because I've managed to get them to agree to a certain marriage, form a joint merchant fleet and successfully remind them that they weren't always at odds through the history stat so again, not sure what I'm missing lol.)
And forcing myself to do Jarrod, Gisette, Woodley and Kade's routes (when his comes out) for the stat boosts is going to be so hard, I am going to be crying tears of anger and frustration the whole time lol. Plus romancing Kade when I love Jasper the most of everyone will feel like a betrayal. BUT WE FIGHT ON -
For Jasper!!!
Good Luck to you as well, fellow Jasper Lover.