I'll just mention that if you're running Thunder with D'Art (as I am) then Astraea can be very useful to get the full sniper shot to land, especially if you're doubling down with the relic weapon for the full 30% debuffs. If you're also running Thor or better awakened-Thor, it also helps with stun.

I usually use Vicissitudes on my extra soul ability slot as I've got a full SSR team - I'm Thunder main - and am near burst damage cap already so don't need no forests, but as always YMMV.

Players with 1 or 2 SSRs in their (non-main) Thunder team can run pretty far with Astraea, D'art, Charles Blaster and the Provisional Forest extra ability.