Like you, I needed comfortable isolating headphones for a noisy office. I finally settled on the Etymotic ER4s after reading a few specifications as well as comments here. Of the ones you mentioned, I only tried the DT770. They were way to big and didn't isolate at all. Plus they would have looked ridiculous and out of place in my office.
Normal conversation is between 40 and 60 dB. The Etys, one of the most isolating phones available, block out 42dB with the foamies. If you listen, like I do, to music with a wide dynamic range, there will still be some times when the booming bass from the next cubicle will be heard above the music. It took a while to get used to taking them in and out, but I don't have any trouble now. I can still hear the phone or at least see the flashing red light. Every office situation and musical taste has different requirements. IEMs are the best compromise for me. I'm sorry I delayed trying them thinking they would be uncomfortable and too isolating.
The Ety ER6 is less expensive and should still provide very good isolation.