I'm assuming Paula has HP as her affection bonus, so she probably has higher HP than Odette. You don't want your mages to be hit by the tengu's lightning though. If you have Metus out, just put her skeleton tokens where I placed my oni tokens (the red guys) on the right and left side of the map. The first tengu appears on the right, so place a skeleton there and once it is killed, put the other token on the left side instantly. After that, it should be fine. Maybe place out Metus first and then Odette? Until both tengus are dead, you will need at least one free deployable unit to deploy your skeletons.
If your ranged dps is too low to kill the guy, bring more units I guess. The headless oni makes 1-2 laps around the bottom square area, so it should give you enough time to kill him and his drunk form. And there is no need to tank the guy. Just wither his HP down with your ranged units. Kokoro should be used to stop him for a small amount of time to allow your other units to kill him. If that does not work, bring a ranger. I believe their traps don't count towards the unit count, so you could freely place them after placing all 8 of your units down.
Thieves are usually used for their non-unit item drop boost passive. These include the items for collection events and possibly affection/trust items. No one really deploys them since their ATK is lacking. Their passive also boosts the ATK and HP of mobs in the map, so if you want a good challenge on maps you call "easy", bring them with you. The boost percentage depends if they are non-CC'ed, CC'ed, or AW'ed. 2nd AW'ing applies too in the future.