Endgame optimised Build for Banshee.
Note - You are expected to run a decaying dragon key with this build, as then silence and breach surge restore enough shields to regain full shields.
This build is capable of surviving and demolishing enemies hours into endurance missions, due to the [Rolling Guard] + [Brief Respite] combo. to supplement this survivability and damage you infuse breach surge with provides both (via CC and multipliers).
[Savage Silence] is a personal preference mod, I use it as it allows me to gain stealth damage multipliers without having to breach surge enemies first, but if you don't want to rely on slash procs to kill heavily armoured enemies, you would swap this for [Sonic Fracture].
To survive you will want to have silence active 100% of the time, and only cast Sonar after casting breach surge first to create an opening that allows a few casts.
Due to the stacking of damage multipliers guns can be used at even very high levels. However, due to the fast-paced and high-risk nature of the build, I'd advise against it, as melee's let you set aside more of your brainpower to monitoring shield gating.
As for weapon advice, anything that has damage over time to continually proc surge sparks.
If you want to invest more forma, primed sure-footed would be a good option but I've not ran into issues without it as enemies that get close enough to do a knockdown attack get either staggered by silence or blinded by breach surge. the main advantage of sure-footed would be allowing you to use weapons like the bramma without risk.