Seeing as there's CD between skills, you'd have cast time of 4sec+ to make a combo of 4 mudras. So my guess, there's just 3-mudra-combos, so it's like standard combos.
They would need to be quite strong, or it wouldn't be any point in using them, or your DPS would drop a lot.
But might be something along the line of BRD loosing dps, with ballad/paeon.
We'll see...most NIN will be really bad though; more so than most DRG, currently