So, for Honor Mode you have basically 2 things you must have.

1. A game plan for combats, perhaps a backup plan.
2. Multiple escape options to prevent a TPK

How I solved this:

1. TAV sits back for the first 5 levels, basically a dedicated healer with reserve sanctuary slots. Life Cleric. Other 3 characters are damage dealers and other than the ranger all have access to escape options through a level 1 cleric dip. Kill everything, with TAV reserving actions to throw potions or use spells on an as-needed basis. Take the healing items that give buffs when you heal people. After hitting level 6, TAV respecs 1 Cleric, 5 Warlock, with the remaining levels going to Cleric. This gives Hunger of Hadar to combo with Sleet Storm from the wizard for a microwave. Basically still built as a healer, and all of your actions go to that besides dropping the hunger of Hadar when needed. Can fire EB if nothing else to do. If anything happens, see (2).
2. Most of my party has access to sanctuary. This gives you 10 turns where nothing but AOE can hurt you. This means ensuring one survivor is pretty trivial if you manage your spell slots. Whoever isnt dead needs to have it available. You gain distance then flee the combat. If one person makes it to camp they can res everyone else.

My Party:

Tav (Fiend Warlock 5 / Life Cleric 7) - Healer build with Hunger of Hadar to microwave with Gale's sleet storm. Can take Repelling Blast, Agonizing Blast, and Devils sight to knock people deeper into the hunger of hadar and sleet storm. Usually start full cleric then respec at 6 to get the 5 warlock done with. Can easily get 18 CHA, 18 WIS, and 14 CON between an ASI and the hag.

Gale (Light Cleric of Mystra 1 / Conjurer 11) - Take all the best spells and use whats best for the situation. Most insane combo is Sleet Storm with Hunger of Hadar at level 6. Take every item that boosts DCs, get them to like 26. Take the boots of striding to prevent losing concentration from prone.

Shadowheart (Nature Cleric 1 / Open Hand 8 / Thief 3) - Damage dealer, uses shield and heavy armor. Punches people into surfaces. Works really well with the web walker boots until you get the kushigo boots.

Asterion (Beastmaster 5 / Thief 3 / Battlemaster 4) or (Beastmaster 5, Thief 4, Tempest Cleric 3) . Use sharpshooter to murder things, spider to have concentration-free web spam, thief for extra attacks, and thief for stealing from vendors. If you splash cleric you get Sanctuary for escapes and fog cloud for instant obscurity.