Only extrapolating from what I have (shield/nrg and sr/claws tanks,) I'd bet somewhere around the 4 min mark... but that's pretty much a WAG.
Edit: Just got a 3:20 on my very unoptimized nrg/sr brute using ET-Long, TF, ET-Short, BS, PAUSE, repeat but also not a procmonster build. Really should build that nrg/shield scrapper some day.