Generally, “effect” seems to be their way of grouping buffs and passives under one umbrella. When you see “fury effects” for example it means regular buffs (like Angela gets) and fury passives (what Titania receives).
Since it's a case of regeneration causing better bleed accuracy: Bishop regenerates but can't inflict bleed; Apocalypse only regenerates in the first second of the fight.
So it's not really very useful for them.
It might theoretically be helpful for Platinumpool if he draws the right cards, and would probably work to increase the chances that Namor will Inflict bleed, at least on his Specials.
Other than that, I think it's really only going to specifically be helpful for Wolverine-type champions.
If you put it on Toad it works, not for the bleed part, but you can switch the rune to increase debuff damage. Sauron also benefits from it, so does Sabrertooth
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So it's not really very useful for them.
It might theoretically be helpful for Platinumpool if he draws the right cards, and would probably work to increase the chances that Namor will Inflict bleed, at least on his Specials.
Other than that, I think it's really only going to specifically be helpful for Wolverine-type champions.