[Squigle D'Muerte]

Gagetter's can make the Lava Lamp (hypnotic lure) very early in the game (as soon as you can make it to Tryton) and it can be a HUGE help. I ignored it for a long time to my regret later. I call it the "bug light" since bugs seem to have no resistance to it at all. Trigger in first round and opponents move to it and stop. This allows you to make ranged attackers move right up to your group caster stop casting and can make melee attackers leave or stop attacking. It can occasionally take out the entire force attacking you by stopping virtually everyone from attacking. There is a bug in it so that every 4th opponent will run away from it for 1 turn instead of toward it. But at least it isn't attacking you and it gives you time to deal with it's friends with repeated area/cone of effect spells.

If you have 1 healer and a few "backup healers" (Valkrie, Ninja, Ranger) use the backups to do all the healing after combat and save main healers spell points for next fight. This also trains up your backups without making them miss combat rounds. Main healer will train enough between combat and finishing healing after backups run out of spell points after combat.

CHEAT:
Pathing Bug in game allows you to fight without monsters fighting back (at least it has done it when I have tried it). When you "zone in" to a new area they can't get to you for some reason until you move. So if stuck lead them back to zone in by running during combat until you zone. Heal up and zone back in. They will be a short ways off but unable to close or run away. I haven't tried this everywhere (as I prefer to play straight up) but found this by accident when swamped by opponents immediately after leaving monastery.