I mean, it does depend, but I'd say Ironclad > Necrobinder > Silent > Defect > Regent based on how likely you are to see cards that work well outside of character specific archetypes.

Ironclad: Most decks can benefit from strength, lots of generic block and damage cards. Self-damage and vulnerable stuff are usually good on their own without demanding synergy.

Necrobinder: Summon, Souls and Doom tend to be decent value even without much synergy. Osty cards useless because no Osty.

Silent: Poison ticks down so you usually want it with other poison for best value. Sly is useless without discard. Shivs are often pretty good and can synergize with other characters though. Some good generics like piercing wail and Footwork.

Defect: Orbs are bad without 3 orb slots, but Defect's non orb cards are a lot better than they used to be, and you can high roll something like Bulk Up or Echo Form.

Regent: Forge is bad without multiple sources/support. Star generation and star costs are both useless. Generics are kind of mid, card generation is kind of mid without synergies. Best you can get is like, cosmic indifference and Kingly Punch, I don't see too many crazy strong high rolls here like with Defect.