Octopath COTC Character strategy: Theo
10TLDR: Use Theo regen on the NPC's broken turn. Since the NPC acts first, this ensures that everyone who gets hit has regen. Pair him with a slow ally that nukes on the same turn as the break or an ally that only needs to act the turn after the break.
Theo is a very powerful healer in Octopath COTC right now. Looks like he gets outclassed later in the game but some of the strategy patterns are the same.
His ability to extend the regen by boosting it (instead of increasing the healing amount) is very powerful, as well as his healing applying to the whole party every time (unlike Agnès).
Since he can't heal the unit in his row, the general strategy would be to equip a regen item like Beastly Scarf in the unit paired with him. However, I argue that using a slow nuker (potentially mcontrolling speed with items) or a post-break shield breaker are also viable strategies.
0:00 Theo's abilities
0:35 Attack skills
1:08 Regen skills - Esoteric cure
2:04 Relevant accessories: A4 accessory and Kota's gloves
2:50 Pairing allies: making sure they are always safe