Basically this is how I feel about it, as I've made clear before. The setpiece is pretty nice, but the forcefields keeping you from interfering drag the whole thing down.
Oh right, and I forgot the stupid fucking forcefields don't even lift immediately after Mahnya's death. You just have to keep on waiting for the game to see fit to let you do things.
"She's a really useful hostage, you see. That's why I'm going to do absolutely nothing to use her to keep her allies from murdering us all."
Eyy it's my girl.
Let's instead discuss the implications that this is a recurring trope for Kaga.
Exactly zero, that's how much. Not even combat quotes, like many bosses in Gaiden. Lamia is the first female villainess to get any characterization at all.
...And, truthfully, as far as minor hench(wo)men in this game go, she gets more characterization than most. For the most part they're either "haha bad brigand", "haha bad mercenary" or "I'm just a general guy," but Lamia takes an overt pleasure in being an asshole that isn't there for the rest. More "haha evil mercenary" than "haha bad mercenary." Her brand of arrogance also feels different - a bit more subtle, and mixed in with some sultriness. There's also the fact that she has an all-girls band, which is a pretty unique tidbit.
What I'm saying is, it's something. Puts her roughly around Clement as far as bossmen that actually have a personality in this game go (though I'd say Clement is more interesting due to the more grey nature of his situation). Worryingly, it also puts her ahead of more major characters like Lungbait and Report.
tl;dr: Lamia cool.
"Dragons are truly fearsome beasts. I can't believe we survived this battle. How can we ever win against beasts such as these?!"
"Lord Roy, he didn't have a ranged weapon. Even Damas was harder than him."
"But, Elphin... Dragons!"
"His name was Ein, Lord Roy."
I agree. It's nice that Rahna's nice. I'm glad she got to live.