If you play without Valkyrie, you earn souls at something like 1/10th the rate per game. Souls in great numbers are so important for progression that this is just too high a tax to pay for exploring the design space of teams that don’t use her.
It’s cool to have a troop that boosts gain of a resource, so that a player can employ it if maxing that resource is top priority for them. But a 10x difference is over the top for the purpose. Vlakyrie could fill that role purely via her Necromancy trait (as could other troops with that trait), giving a 1.5x return instead. That’s more like what Alchemist delivers now. (Make Alchemist deliver 200g per cast with a ceiling that allowed that to 10x your gold return per battle and he’d be comparable to today’s Valk.)
And then of course boost the baseline souls-per battle to balance for Valkyrie’s skill being something that doesn’t generate souls. So you can hit your difficulty’s souls-per-battle max if you have, say, two Necromancy traits on your team, but still earn around half that in souls if you play a team without that trait.
I know you’re doing stuff with skills for 1.0.9 so maybe this is already in the works, but what do I know?