Those three party members are honestly probably the most stable throughout. Beast is generally considered the most forgettable though, but it’s likely a symptom of him not really having anything crazy going on compared to the rest of the party. Loshe is great throughout, and actually the only party member you can later ask for her opinion on various important NPCs you’ve met.
Fane is very obviously the writer’s pet, you miss out on a lot of background lore without him. Though he was written by Avellone (just without the typical angst his characters usually have), which shows.
I think Avellone also wrote Nok-Nok in Kingmaker, who was also not angsty at all.
Fane is almost necessary for a whole lot of lore. I played as him in my second playthrough, and never recruited him in the first. In terms of lore, arc, personality, and plot satisfaction, I would rank the companions in highest amount of attention given to the lowest:
1. Fane (VERY Significant to main plot, in every Act.)
2. Ifan (Significant to main plot)
3. Lohse (Like Fane, she is fun and "different" from the other companions)
4. Sebille (Her story climaxes WAY too early, otherwise she'd be higher)
5. Red Prince (He was my Origin character in my first playthrough. His plot is so aggressively tangential to everything happening in the game that it's laughable. A lot of companions have 'tacked on' stories in RPGs, which is basically the rule for a lot of Bioware companions, but in a game where several characters have plots that directly relate to the major events and characters of the game... it's really bad)
6. Beast (In the reverse of Sebille, his story isn't covered that much until near the end of the game. His plot does get good, but it's only near the end.)
GM, I'd advise swapping Beast for Fane before fighting Alexander. Unless you're fine waiting a long time for real payoff on Beast's story. Fane is relevant in every Act.
Edit: If Sebille's plot didn't just... stop, I would place her between Fane and Ifan.
