Bank is a map where you will find few shotgun wielders - line of sights are extremely long down hallways, in the garage, and in the Big Room. It's difficult to justify a competitive CQC strategy unless you are playing vault.
Spawn killing can be an issue at times. Watch the windows if you spawn by sewer. Not enough defenders take advantage of peeking from these windows, I think.
Spawning on the garage end opens you up to a cheeky peek from in between the front door pillars and the barricade. Defenders (Jäger) can strafe in and outside of the door without alerting attackers. Hide behind the cop car for a few moments after spawning and wait for the peek, then continue.
Bank is a great roaming map, as most maps lend themselves to be. I find that there is a LOT more glass on the ground than other maps, so be careful with your steps as it is louder than you think. If you are roaming to CCTV room from Skylight, be wary of that damned metal detector you have to pass to go down the stairs. It can ruin surprises, so act fast, or wait for gunfire to mask your sounds.
Always drone out the garage before entering. If you get killed without droning it is 100% your fault and you should feel terrible for playing so sloppy.
For some reason, everyone is convinced either Basement level or Top level are always the best locations to defend. In my opinion, Open Area/Kitchen are fairly easy to lockdown.
Always check the elevators. Always check the elevators. Always check the elevators.
Bank has little verticality to it. Most attackers will be forced to drop through hatches or ascend/descend staircases. A few interesting spots include The CEO office which can be attacked from below in the Archives room, flushing out those pesky defenders behind the deployable shield in the vase corner. The Vault lends itself to zero roof destruction, except for multiple hatches.
About those metal detectors, turns out if you melee the button on the physical detector part hard enough, they won't go off. Not sure if wasting your time staring at a thing on the ground leaving yourself open to peeks is worth being "silent" though. Just a neat little thing I thought I'd share.
Pretty interested spot I found in this map, its fairly obvious but not many people know about it. When defending the basement head up to the third floor (shotgun required ). Shoot out the hatch in the closet, and then the one directly below it in the office. From the closet you can see down into the tv room without anyone expecting you all the way up there. Also, people tend to walk in the office to use that drop down (especially in bomb ). I can't tell you the amount of C4 kills or just regular kills I've gotten up here. I like using Valkyrie the most so I can put a camera in the tv room and see it but pulse, smoke, caveira are all good choices as well.