Best I can recommend is find something else for FL4K.
I personally run a re-charger (instant recharge on shield break with cooldown) and Last Stand Otto Idol relic (short invulnerability when below 50% with cooldown and 18% health restore on a kill).
FL4K doesn’t have that many shield buffs so you may be better off playing into their other strengths.
Oh, and make sure it’s not a loot expander deathless, that increases all ammo, health and cash drops by quite a bit and in this case will flood you with vials. Not good for a non-bloodletter Deathless build as they’re wasted.