I assumed it was lore-based that I never see the Nevermore in fleets; the ship is decently fragile when flux is mismanaged and very susceptible to flanking, not to mention its massive deployment cost (high CR Per Deployment with massive Supplies to Fully Repair). I figured it's a "special ops" ship. But, I've also yet to fight against Blackrock, so I haven't paid much attention to their fleets specifically. That said, my Blackrock tends to wobble between 0 and 4 in stock pretty regularly.
When I played low-tech (and even on higher techs to a lesser degree) I felt the crew salaries made me use a more "thinky" procedure; my flagship and special ships get elite crew and any extras that get promoted get plopped in storage for future replacements in case one of said ships gets dunked and they get replaced with greens. Crew rotation becomes part of the routine when docked at home for a resupply and refuel, and I think that's pretty cool instead of just slapping in the most elites possible. You can even make a tidy profit from selling the elites instead.