Thanks for the replies everyone, kinda sad to see Black Sun is quite underwhelming, the concept for their faction is awesome, the execution is well... lacking.
Its more of a case of growing pains then bad execution. Type-005 and Styx were the first models on the scene for BS. Which like many of the other factions had their pluses and drawbacks. Only BS has other filled out Org to compete against.
Arkham might still be workable once BS gets more guardain type units like maybe Bridget or Velvetaire. Plus he is a cheap Controller with some rather interesting skills so he might be more useful as more undead come out. Much like Genma first seemed lacking but is getting better with each Summon Creature that comes out.
The same might be said with Kingley, who still works in that he is the toughest living controller out there. Remember Promethia is the number one target in any Undead BS party and she is pretty squishy. Might best to think of him as more a front-line warrior who can survive being up there with the rest of the Undead shock troops. instead of trying to stay far out of the fray.
Styx might cost too much and too dependent on Promethia but if you got 25 levels to spare he can be good as a bullet and prowler flusher.
Type-005 you can already see them trying to improve them with Plot cards and other units. If they continue on that path Type-005 might be salvageable.
Plus all the units after Kingsley look quite impressive. Deimon, Nk-X non-leader, Type-012, Type-009, and Lynn Steiner.
They do have one of the top leaders in the game in Clover. And many of those Undead types you can take more then one to fill out your ranks. Plus they now cleared up Free Agents allowing Shinobi to be BS living agents makes that now a viable party build.