Just wanted to clarify: I'm not dissing your builds, or your posts. They're great reads and I'm looking forward to what follows.
I just feel it's not a high-level encounter at all in the setup. "Hobgoblins looking to kidnap some people" feel like a 5th level adventure setup, maybe 10th if the hobgoblins are extraordinarily tough and the targets really really important and it's basically a horde of hobgoblins.
Basically, I like to have a rule of thumb (note: not a rule, a rule of thumb);
At 3rd level, saving a person is a minimum.
At 8th level, saving a town is a minimum.
At 13th level, saving a country is a minimum.
At 18th level, saving the world is a minimum.
Basically, I don't think a BBEG wastes time kidnapping some random people. That's what she's got mooks for.
I've gotten a bit inspired by this thread and am currently working (thoughtwise) on a martial BBEG, and this is the basic setup:
Half-human blood war veteran who now acts independently both with having her own army that is dangerous enough, but more importantly she acts as a negotiator and advisor for demons. The party need to stop her both because she has a big frakkin' army threatening to take over the world, but even more because she has managed to get demons and daemons to partially cooperate to kill off devilkind, both with their own ulterior motives. If the blood war ends with demons as victors, what would happen to the material and upper planes? Chaos, that is what.
So the party needs to assault her extraplanar fortress. They know it's trapped, they know it's guarded, they know she has allies.
Currently I'm just doing it as a creative exercise because I've got lots of time on my hands with work being heavier on my back than my mind, but if it turns into something written I might post it here, or even make it a short PbP.