On the subject of how shield blocks are being calculated:
The calculation to include blocking is a VERY rough approximation as the usefulness of block dramatically varies from fight to fight. For the sake of the maths here, it was assumed that the boss attacks with speed 1.0 for approx 1500 damage on the tank.
My main goal was to find a workable solution for integrating block into tank points. Although it is a complex subject, yes, I felt it was utterly wrong to just ignore such an important part of tanking.
Obviously, with the way I calculate it, it undervalues shield block if you are fighting against stuff that doesn't hit as hard or as often. For an extreme example if you have 30% block and 200 block value and are fighting something with that hits for 200 damage, every 3 seconds, then you'll have 100% mitigation with shield block ability. Similarly, if you're fighting something like Patchwerk, it overvalues shield block.
There is a case for reducing the scale on the numbers slightly though to 1.5 and about 1200, so will think on that.