If you don’t have a debuffer (Grimm, Tiburtus) yet, definitely go for Gormek.
If you’re looking for a more solid defense, and only that, go for Colen.
If you’re looking for a versatile hero against titans and in raids, go for Scarlett. She hits fast and hard, and has an attack debuf.
Lancelot looks cool on paper but he’s squishy, and half his special is wasted if you pair him with Boldtusk. A niche case for him would be two slow heroes by his side, making the best out of his mana buff. But working with the slows isn’t everyone’s cup of tea.