So now we're getting a better idea of who the PCs are and what they bring to the binding, a thought I'd like to throw out there:
This binding was rushed. It's something thrown together on short notice from the best (?) candidates available, with some expected parties or candidates refusing the arrangement or failing to meet the deadline.
- Jorik's death put the finalisation of this binding on a very real and sudden deadline. Pressure applied by his patron(s) forced the timeline up considerably.
- Grimvine's candidacy would have been a problem for some and may have caused some individuals to refuse to take part.
- Zakarr sounds like he could have good reason to drop everything and seek sanctuary in this duty.
- Sebhata is an asset who had outlived her usefulness in her previous position, one who could be quickly and easily reassigned and disposed of.
- Kaltos is an obvious stabilising force meant to help balance things out. Maybe he was already set for this binding, or perhaps Sigmar chose him for the role after seeing the direction things were headed.
- Arthenadon might have been a package deal with Grimvine and/or as a second Sylvaneth could reflect a lack/loss of candidates from other sources.
This has the feel of something a bit messy rather than a very deliberate fellowship with carefully curated members, and between Jorik and Grimvine we've got decent explanations for why the powers that be might have been stuck with second-best rather than their preferred choices for the binding. We're a product of circumstances rather than the bright and shiny chosen of the gods, and we're going to carry the weight of proving this wasn't a mistake.