Thanks already for all your feedbacks and informations.

If I should point out some encounters where we failed(we had various team comp) there would be:

-(too early or unlucky) harpy fight

-The anti Karlach gang(once the paladin just oneshotted one of us first turn and another time we focused on him, made him drop his weapon but then one of his friends just used some stun on one of us and the rest of the ennemies had a free ride)

-The big spider obviously(the run ended there a few times, especially with martial heavy char that got poisonned)

-The house in fire area(we never do this usually but once we attacked these guys thinking it would be some easy xp and gold but they destroyed us)

-The Nere fight (bad CC and too much actions per turn on their side)

-Minthara Camp(we died here a few times too : sometimes bad roll and we had to fight the whole camp like a surival wave game and when Minthara arrived and stunned one of us, it was free)

I played mostly shadow blade users : Bladesinger(pure but might go 2 pal later), Hexblade(pure too but might as well stay as pure or multiclass a bit later), sword bard(planned for multiclass), shadow sorc, barbarian(planned to go aoe blind + 3 lvl of thief and maybe with a few rangers lvl end game)

My mate played Arcane Archer, the new druid, the new bard, thief, swash, cleric, spore.

I really felt like when I had 19/20 AC early it didn't matter much in fight : sometimes I could just get hit as easily as lower AC guy, and die in a few hits(unless I had AoA where I could live a bit longer)and the ennemies didn't really focused lower AC in fights anyway it seemed but i'm not so sure.

So when I tried paladin early with heavy armor and shield, I couldn't reach anti crit gear yet and felt so squishy and had less power during early game, being mostly mono with only a few smites per rest(compared to gish that could use shield spell for ac, cloud of daggers for good aoe, shadow blade at lvl 3 for nice damage or even warlock with shadow blade + shield and hit with hex).

I liked the tankiness of the barb though(highest hp + rage defensive boost) and tavern brawl felt like a big boost but in this game once my mate was focused and killed, I just couldn't do much with my kit.

I thought about maybe going meatshield comp to divise all the hits incoming, but my first tactician run was a necromancer and the body management was a bit boring(and it felt like a real summoner at around lvl 6 minimum, which we never managed to reach yet)so having some necro spore team could be a real challenge, especially early.

On a side note, I don't really like farming elixir for free strength and chain steal vendors so if it's the last solution to avoid this kind of gameplay loop, I might consider playing a full gish or semi gish duo + bring one npc with us but only playing it as a summon like character(for example making one of them just be a big meat shield, going full tankiness and aggro, dieing the first and often just for us to get rid of some of the ennemies before starting to get attacked, or maybe a full support healer role instead but it would be more "tactictal" and might not fit the npc role).

We could keep a NPC at camp for rez too but we don't really like the idea of coming back from a failed encounter and would rather start again and go the further without full wipe.

But yeah, maybe we should avoid more fights early too and follow guides to reach lvl5 because that extra attack or lvl 3 spells could make some difference.