Kinnea

You could try to make her 2H with the buffs for other people. She still won't be the greatest in terms of damage, but alas she can make your other damage dealers stronger. I'd go for Glorious Beacon-> Inspired Beacon (for +40% damage increase), Virtuous Triumph to regain resources, Exalted Focus for Accuracy/Crit to Hit. Shared Flames to once more increase the damage for the group and maybe Zealous Exhortation or Hastening Command, which you prefer. She won't be a great damage dealer, but she'll increase your overall damage by a lot while likely being able to hold her own. As for Xoti as a contemplative... At level ~8 I regret having her as a single class Priest, because with Swift Flurry and certain bows she'd do great'ish damage next to being able to buff. At level 16 I was glad I had her as a single class Priest, because Spark the Souls of the Righteous is a very strong spell that managed to do some 200'ish AoE damage every 3 seconds for a minute if empowered and doesn't friendly fire.

Near the port there's a cave to explore!

I mean, Mass Effect 2 was one of the highest rated and most beloved RPG's of all time. And it's actual, 'MAIN STORY' is literally 3 missions of 20 minutes each. Anything else around that is just finding companions, loyalty missions and side missions. But the companion and loyalty missions are written engaging enough that you don't care about the main story being literally 3 missions. I don't think the length of the critical path has anything to say about the game being entertaining, engaging or anything else.

Multiclassing feels more powerful early game, where as single classes, especially casters feel way more powerful in the late game. Xoti for example. I made her a pure priest solely to buff and heal. Around level 10 she wasn't as useful anymore and I regret not going Priest/Monk to have the Swift Flurry so she can do more damage. At level 16 I got access to Spark the Souls of the Righteous, which is such a hilariously powerful spell that even non-empowered ended all fights within 10 seconds. (For those that don't know, it places an AoE on every ally/summon it hits that ticks for 15-25/*30-50 damage in an AoE every 3 seconds for 30/*45?60? seconds.) You hit that on your 2 melee and 3-6 summoned minions, suddenly everything around you just dies. Imho, Multiclassing is more powerful for longer/sustained fights especially with melees and creates more powerful tanks, where as single class is stronger for casters and shorter fights. Then again, the empowered spells will likely make every fight a short fight, so that point is relatively moot.

I think it depends on what you want to do more so than anything else. Do you want to have additional fire damage? Paladin and Chanter can offer you that Do you want to have fire themed buffs/aoe while in melee? Paladin/Wizard or Paladin/Priest of Magran If you want to be a caster, I'd however go pure Wizard or Priest of Magran as the level 8/9 spells are incredibly powerful, especially if empowered.

Pallegina was my main tank, a Herald too. With the things you named - Exalted Endurance, Greater Regeneration Ring, Lay on Hands and Her courage thick as steel/Ancient Memory. I think at around level 13-15 my party stopped needing any heals other than the occasional off heal that could've also been solved with a potion. If you use potions on your tank (Which I didn't cause I'm stingy) you could probably do well at a lower level than that as well. So a Herald can definitely handle tanking+healing. If you only want to use the Herald as a secondary character, I'd probably go melee to keep the tank healed and alive. You don't necessarily need to pick a subclass for your chanter either, as chanter in itself becomes increasingly powerful.

Personally I used Saint Omaku's Mercy with the recover reset on crit. She often went on 5-10 crit streaks, especially if buffed with accuracy and a hit to crit pet.

That's what I played, sort of. I went for a Devoted/Paladin(Kind Wayfarer). Stats were like 18/8/18/8/8/18 - With Deep Faith you had crazy amounts of deflection and with Mob Stance/Zealous Aura/Disciplined Strikes you dishes out the damage. There are probably way stronger builds later into the game, but this was strong from the first level and incredibly powerful during the mid game.

I'm not sure why everyone is talking about Frostseeker. I've tried it, but I much preferred the bows that recover on crit. https://i.imgur.com/ghgyONq.png And that's without swift flurry or disciplined strikes