I think Lady Locke and Sargosso could use buffs to make them more desirable.
If lady Locke were bumped up to fast mana, I think that would make her very desirable for her cleanse. Decrease the amount of damage she does, but make it so that if her DoT gets dispelled, she inflicts 50% of the damage it would have done immediately.
For Sargosso, make his 80% health gain reduction non-dispellable and have him and his nearby allies gain 25% attack for 4 turns.
Cap’n Kesteral isn’t bad, but he lacks that intimidating factor. If they gave him a mana cut after he struck his 3 (up to 3) victims, I think people would be more excited for him. However, since he is based off of Jack Sparrow (who is notorious for pulling tricks that cause his enemies to damage themselves) a self attack or blind may be more fitting, and, depending on its strength/potency, could affect all three heroes hit or just the center hero.
How’s that for a christmas song?