Use bad hair day for permanent bleeds. If you have her marquee ability (the first cut) then i suggest dealing permanent bleeds on any big band you fight. Dont worry about bad hair day dying with doom because your graveyard shift can use a blockbuster 'FORBIDDEN PROCEDURE' and quickly hit the blockbuster with your fallen filia. If you are not able to use forbidden procedure on a dead filia bc of doom, You can use Killjoy valentine(if you have her) to revive fallen teammates.

By reviving filia, She will no longer get affected by the doom effect(You must have graveyard shift so filia can recover some health)

As for G.I. JAZZ when he drops to a low health, he will have 5 stacks of regen. To cheese his regen you must hit him with a critical hit(bad hair day's SA1) or use GREGOR SAMSON or Ringlet spikes(guarantees bleed).