I'll bump this thread as I ran into this problem numerous times bleeding the rear brake (V4). What eventually got it was to unbolt the caliper from the rear post mount so the bleed nipple would be the highest point of the actual caliper. If you don't do that, air will get trapped in the caliper, resulting in bubbles and that mushy brake lever with an excessive throw.
On some bike, like on my bronson (V3), the postmount angles the caliper the wrong way and points the bleed nipple downwards, making it impossible to get a proper bleed. It took me awhile to figure that one out and to actually detach the caliper from the post mount to get the bleed nipple in a proper orientation! A small bump in the road of what I think is the finest pair of brakes out there right now.