Basically, before Turn 4 you don't really need it, Turn 4 and beyond it is a really beneficial upgrade that can make or break a run. Possibly not so much for WAR, though I imagine it'd still be better than regular Bravura for that turn. Otherwise vitality and accuracy are what you want, so prioritizing AF2 pieces before Turn 4 is a good idea. Hard to plan for RNG drops in Coil so best to just upgrade what helps the most for where you're at.