There's a multitude of reasons why Citi has so many VP's.
They're too quick to promote AVPs, and too slow to promote VPs. So most people (IC's) top out at the VP level for their career (the salary band for VP is fairly wide), unless they move into the management side. There should be a lot more AVPs in the company to have a healthy level of junior staff being trained up to become senior staff.
There are constant headcount reduction/justification exercises that limit group's from growing: no req approvals even for C11/C12s, or groups only want C13s to replace a C13 that left, so we hardly have any new graduate hires that then would grow organically in their career. And when new hires come out of the graduate program they're automatically at AVP level (and not C10/C11), and then fast-tracked to VP after 2-4 years, or they jump ship. That's too quick for a junior staff with less 5-10 years professional experience to be promoted to VP - they aren't Sr analysts yet.
And if you have no new hires, then after 5-10 years your group turns into all VPs and stays that way for years until there's a re-org or some management leaves and 1 person in the team gets promoted to become a new SVP.
I would agree that the salary band for C12's is a bit low on the high-end to be competitive for people in the 5-10 year experience range. Everything should shift right more to keep up with the industry.