So I was pretty nervous about getting through the game on tactician difficulty/honour mode after reading about the difficulty online. I ended up playing through tactician difficulty twice, the first time just to enjoy the game and play as I wanted, the second time on honour mode while getting all missable trophies. I found out it's actually very doable. A few things that helped me in my playthroughs 😁
Number one: be very diligent about backing up your save file. Never allow deaths in the middle of the enemy's turn, unless you have a recent save backed up online or even safer: a back-up on USB. I lost hours of progress twice because I got stuck in an inescapable death loop.
My party consisted of 2 mages (Geo/Fire/Witchcraft + Aero/Hydro/Witchcraft), a ranger and a tank. What I would do differently: My mains were a mage and ranger (while Madora tanked), which made my mains much more likely to die in a few hits. Having a tank as a main is much safer!
Go through the order of quests as intended, never enter areas you're underleveled for.
Maximize experience by winning the rock/paper/scissor encounters, then still kill the NPCs when you're done interacting with them for extra XP. Quests like war of the stone and closing the rift can also be completed with way more experience by engaging more enemies. Closing the rift specifically nets you way more experience if you destroy the blood stone while engaged with a bunch of demons (they are killed instantly when the stone is destroyed).
Maybe an obvious one: be smart about using your surroundings and tools at your disposal. Carry oil/ooze barrels with you, teleport enemies/bosses away before the fight, and use elemental grenades/arrows as they are super powerful.
Have multiple characters that can charm the enemy using charm arrows, rapture and love potions. This makes fights with orcs/humans/goblins really easy.
End game spells like meteor strike, thunder storm, hail attack, arrow shower are OP, especially if you have two mages in your party that are able to cast them. The final bosses are a breeze if you spam hail attack scrolls (I had about 8 of them at the end of the game). Guaranteed to apply frozen and do a ton of damage.
Use multiple characters with summons for an extra line of defence (another reason why two mages is a good idea, plus give Nick to your tank/ranger).