I'm glad you've enjoyed it for the most part!
as for the island storyline, there is no 'filler' arcs as far as I'm concerned, Nephilim is about the main character being an adventurer and exploring the entire world of Midomir and meeting a large cast of characters.
Taron and the avenging of our parents is just one of many plotlines, you will however get your conclusion to the Taron plotline at the end of Season 1 (Chapter 7)