The REAL reason Lahabrea has shallow writing compared to Emet-Selch is back in ARR they almost certainly didn't have the Ascian lore fleshed out yet. I liked him anyway, though. He was the Thancred of the Ascians; always so cool despite the fact that he was constantly jobbing.

I wonder if he's actually gone, though? He was struck down, absorbed into an Eye of Nidhogg that was later drained to summon Shinryu who also died and then the inert Eyes were destroyed by Estinien. Could he have "survived" that? ...I honestly don't know, I'm asking. Echo can do some weird stuff.

....While we're on the topic of the Unsundered, I've always wondered why poor Igeyorhm didn't get to be one. She was the one that turned the thirteenth shard into a void then she worked with Lahabrea and died alongside him but the plot has mostly forgotten her.