Vick asserts in her internal monologues that she is a master of deception and never lets her true emotions through her ironclad resolve. Yet from the perspectives of other people, she's occasionally described as being surprised, annoyed and so forth. She's apparently Not So Stoic as she thinks she is.
Leo'a arc of starting out as an arrogant, badass soldier before becoming crippled and turning into a bitter, cunning chessmaster mirrors the arc of Savine's father, Sand dan Glokta.
The vault at the main Adua branch of Valint & Balk being empty instead of being filled with mountains of money and valuables actually makes perfect sense and is not a sign of the bank's power being a sham. Banks work by lending out most of the money they take in deposits, and only keep a small reserve of cash to attend their depositaries' needs. In the real world, central banks usually establish a minimum legal reserve banks must hold to avoid bank runs, but absent any kind of authority of this sort in the Union, there is nothing stopping Valint & Balk from lending practically all the money and keeping virtually nothing in reserve.
Zuri and her brothers' true identity is foreshadowed in a few ways. Savine recalls that Glokta was the one who introduced them. She notes how surprisingly strong Zuri is in spite of her slender physique. Zuri is absent when Savine meets Yoru Sulfur, someone who could identify her. Savine is surprised that Zuri looks nothing like her supposed brothers. She also notes the many teeth of Rabik.
The destruction of the banks was meant to curb Bayaz's power but it's still an industrialized modern economy. There will be new banks and investments that Bayaz will be able to manipulate. The final chapters of the trilogy reveal that he's well on his way to doing so.
