I found the E3 to leak considerably more than the NX. When I covered the top vent holes on the E3, it leaked much less so that's the majority of the leakage. For my preferred listening levels, E3 would definitely bother my coworkers.
It does depend on how noisy the office is, and how loud you listen to. They're not the most isolating, but they're still leagues ahead of any openback.
At modest levels, in an average office (with background noise, people chattering, airconditioning humming), you'd need to be pretty close to hear anything.
If you work in a morgue, and like death metal, then yeah... the bodies are going to sit up and dance.