Wheel of Time series is great. I'm reading book 5 now
As for having some of the tanks mitigation and some avoidance... several other mmos have tried this (most notably EQ2) and it has NEVER worked out.
An avoidance based tank is prone to spikes in incoming dps (both spikes of increased damage coming in because they miss a dodge or two, and spikes where they get a good run and avoid everything). Mitigation is normally very predictable and stable.
The problem is that when an avoidance tank gets a good streak and avoids a bunch of attacks, it saves the healer some mana/power/whatever. But that can be immediately followed by a bad streak which results in a quick death for the tank, no matter how much mana/power the healer has.
In EQ2 a monk was supposed to be a tank on equal footing with the warrior... but it didn't work out due to the mitigation vs avoidance problems.
As for the idea of using a staff to block... would be great if they could do it in a way that is balanced with weapon/shield combinations. Yet another option to individualize your character.