Was the exhaust manifold on when you installed and torqued the head? If so, the ears of the manifold might have caught the back edge of the block. In such an instance, your head would not seat to the block, but you'd be able to toque it. The head would be kept off the block, preventing the gasket from sealing.
There is quite a bit of play in the head bolts on the VW diesel, so you have to actually center it and hold it in place when you snug the head down, and be certain that nothing is binding.
I once tried to install a milled head with the exhaust manifold on, and I noticed that the ears (where the manifold bolts to the head) of the manifold projected beyond the surface of the head, and were "standing" the head off the block and preventing a clean mating surface.
The ONLY way you'd have coolant pouring out of a head is if you did this (above), or had a cracked head, or had something between the head and the block. Not even the crappiest headgasket will "pour" coolant out with 90 lbs on the bolts (BTW, I think you can go even higher). Nor will any warped head "pour" out coolant with that much torque on them. I'm sure it would when running under pressure, but not when filling it up.