Thanks for the input. Question... Given Paladin-Wizard-Cleric as 3 members of the party. What would you take for the 4th?
Sorcerer, Ranger, or Rogue?
For my own party, I like Ranger with the lowlife background, they can handle the rogue skills and I find they handle better in combat than a Rogue. Rogues need to flank and use advantage to be effective. Rangers might not have the sneak attack damage but they can dish out a lot of hurt plus have heals and other utility stuff. That's my reasoning at least. They're also more defensively sound than rogues, having higher HP and AC from being able to use a shield and get the defensive combat style.
I don't think the Rangers are better for combat than Rogues beyond the first few levels, generally speaking. Flanking and advantage are easily achieved through Cunning Action (hide, dash and disengage on bonus action) and they get some serious defensive buffs like Uncanny Dodge levelling up. I often find that positioning is often one of the most important things for Rangers and Rogues. Shadowcasters have access to powerful defensive magic to even the odds even more.
That's not to say Rangers aren't effective. They are pretty strong in Solasta, though very dependant on Hunter's Mark and therefor Concentration. Their biggest problem is opportunity cost, seing as they don't get subclass spells (like later archetypes in 5e gave them) and have a limited number of spells. Their spell selection is also a bit lacking. Often they'll just use Hunter's Mark and the occasional heal.
Overall, I do think Rangers are a bit easier to use, but a well played Rogue will consistently dish out Sneak Attacks and dictate the engagement with their superior mobility. Shadow Tamer Rangers are likely the strongest damage dealers in the endgame though, since they get their proficiency bonus (+4 at lvl 9) on all weapon attacks against enemies with Superior Darkvision, which is just about every high lvl enemy. With dual wielding or Follow Up Strike, that's 12 damage extra per turn for free. 16 if hasted.
Hunters are more of an all around skirmisher, trading down their damage a bit (compared to Shadow Tamer) in return for Multiattack Defense, which is an amazing defensive feature. Solasta buffs it even more than normal, making you immune to attacks of opportunity as well.
I've not had a chance to try the Marksman Ranger much, but it seems underwhelming compared to the other options. For Rogues, only Shadowcaster seem to be worth it. Darkweavers get a poison damage as their late game ability, at which point most enemies are immune or resistant to it. Thieves are... well, not ideal for combat heavy campaigns.
Sadly we can't multiclass in Solasta. A Ranger 5 / Rogue 5 would probably be one of the strongest melee skirmishers in the game.
I would recommend people to try whichever one they haven't given a shot already. They might be surprised.