Star-Blade probably has synergies with getting Sorcery through Philosopher's Wreath, but I'm not sure we want to go there. It's another 7 Arete investment that takes us further from Ruling Ring or Once and Future. But both Bloodslayer and Star-Blade have the potential for death spirals built in, honestly. The former makes our first form tougher, but does nothing to buff the others except for taking A Thousand Cuts so it can stop showing up in our build votes, like a drunken uncle at a family reunion.And this investment in Gown will likely give us more findross stuff in general; given our Pseudo-Grace. Compounding magic systems is something with Incredible power in these Quests and so getting another one may give far better returns than just more blood.
The latter's Pseudo-Grace lasts as long as the Evening Sky does, but we've seen that ablate away in the face of magic damage, and once it goes down we lose a huge chunk of strength and agility. We'd want to pick up Opalescence + Iridescence soon. Maybe even Pearlescence, but we don't have the funds for it. It's a shame Balance didn't get more play, Heedless seems too spicy for most voters' palates and the anti-synergy of Bloodslayer is painful.