Merge. He is one of the best units in the game (Top 5 for sure) and he sits in the highest BST bin for scoring purposes. You want him to be +10 eventually, if possible. Lissa lacks the distant counter and general availability that Hardin brings, so fodder her instead.
Pokemon GO
Fire Emblem Heroes
Fate Grand Order
Dragonball Legends
Dragalia Lost
IV Calc
Heroes