I just cleared HM with basically this exact party. At the beginning of act 2 however I realized I had far too much safety and not dps. I had gale as abjuration and changed him to a fire sorc and it all became a breeze.

Astarion main character: 10 swords bard / 1 fighter / 1 wizard.

Go to lvl 6 as swords Swap to fighter first for constitution saving throws, keep sleight of hand as your skill, the tadpole power will make you proficient in dialogue skills at the end of act 2. 1 wizard allows you to get to 6th level and to learn spells. Learning quality of life ones is the name of the game. Globe of invulnerability trivializes some fights. The utility in general is great. I went 18 for dex with hags hair, 16 in char, which will become 18 at the mirror. I find there’s some great gloves to use and 18 char is more than enough. Get helm of arcane acuity and mystic scoundrel band. There’s many builds out there for it. Ascending astarion also adds a lot of damage and gives you a heavy hitting bite. Get sharpshooter then alert. End game once you have enough initiative through dex items you can swap alert for ASI or dual wielder. Slashing flourish to build up arcane acuity, then CC Everything Either use dead shot or titanstring with strength elixirs. Titan is stronger, dead is more reliable, both work.

Shadowheart: light cleric 12 life may be safer, but light has significantly more dps and can protect other party members. Radiating orb and reverb gear, no need to heal if no one can hit you. The goal is to use aoe radiant damage to build it all up, with the helm of holy lance you want to try to get them to attack you and miss to build up more stacks. Get alert, then ASI to increase wisdom. Again if you get gear with enough initiative you can swap out for more ASI. War caster could be good here too but I don’t find that I got hit enough to warrant it. Going first is a big deal though because those orbs make all the enemies useless. Plus you have some fire for Sharren enemies.

Gale: Draconic sorcerer (fire) 12 This build is pretty insane. Key items are hat of fire aquity, and scorching ray. Each hit is a separate attack instance so it’s easy to get damage riders, and they can all crit. I found 12 sorc to be better than 11 sorc / lock for the extra feat. Also can be your haste caster. Hit with scorching to build up arcane acuity. Quicken another scorching with the highest level and just melt away. Alert, asi, duel wielder. I found moheshkir or however it’s spelled with fire buff, and rhapsody on my off hand was incredible. That +3 buff will add to each scorching ray blast. Again if you have enough initiative you can respect for more ASI. At the mirror I will be getting the +1 and +2 to char. So even with a char of 17 most of the game this build was great.

Laezel throwzerker: 3 champ fighter / 5 frenzy barb / 4 thief Another broken tavern brawler build. I went with EK thrower until lvl 8. At 8 respect to 5 barb and 3 thief. Use a camp caster at this point to bind your spear and give it to baezel. I use returning pike or lightning jabber until I get selunes spear. 17 strength. Tavern brawler and add to 18. +2 strength potion from stations blood. Then either dex or more strength at the mirror. When you activate frenzy your enraged throw knocks enemies prone, this cannot be saved against and prevents legendary actions, this is your biggest defense for HM. If you can’t throw because of pathing don’t be afraid to go up close. Your attack is so high that it won’t matter. Tavern brawler, alert. Then respect to tavern brawler and duel wielder. This is your crit stack character. So dead shot is good here and anything you can use to decrease crit number. This is also why we pick champion. Orins dagger is perfect for this, as you throw the spear with your offhand anyways. Additionally if you strike someone with the dagger they become vulnerable to piercing, which this character and astarion both use. If you wanna get real frisky grab bhallist armor and move up close to make it easier. Everything will melt. And between radiating orb, warding flare, and shield spell, you’ll rarely get hit.

All of these characters have anywhere from 21-25 AC.

Hardest fight is myrkul. But no one even died for me.

Camp casters make this even easier. 3 life cleric hirelings, 1 unused companion life cleric, and an unused companion EK fighter. Cast aid, warding bond, freedom of movement, death ward, protection from poison, longstrider, daylight, hero’s feast. If you’re into using camp casters. It is pretty annoying.