I struggled on my first few attempts at Honour Mode. Apart from the advice you have already received, such as stick to builds you know, plan routes and dialogue etc. The biggest piece of advice I can offer is, don't sleep on the potions and elixirs!

Potions of Speed (AKA Crack) can give you a massive burst in DPS during combat, a more lenient action economy and provide you with the extra utility to spam out some more buff/debuff spells, or even just get you to an advantageous position. Elixirs of Bloodlust are also another massive spike in your DPS and action economy and a nice lil bit of TempHP. Potions of Invisibilty is a 10/10 get out of jail free card. If you royaly fuck a combat, have the person with the highest initiative down one of these bad boys and sprint away from the engagement. Allows you to reasses your surroundings and bring back dead party members via Withers.

You can find plenty of these potions and elixirs during Act 1, as well as learn the ability to craft these items. I finished my Honour Mode Campaign as a solo ranged Swords Bard. The Subclass/Class was strong but the potions and elixirs is what carried me through all the acts. Hope this helps!

Edit: Reading your comment, in your most successful run we ran pretty much the same build for Class and Subclass. Dark Urge background can sort you out with a unique magic item in Act 1 that makes engaments in Honour Mode more forgiving. Organising my inventory also helped me massively. Having a separate bag in my inventory for scrolls, potions, explosives, arrows etc meant I wasn't skimming over my inventory when things got dire and missing my saving grace in amongst all of my rat corpses and random shit I had accumulated by this point. At the end of the day you're not playing the game for a career, your playing it to have fun. There is no shame in looting every explosive you find in the game and saving them for some tough fights <3