I think Ice does things in a weird and more difficult to quantify way than almost all the other sets. It has DEF for sure, and crazy cold resist, but Chilling Embrace (in addition to being a taunt aura and a movement slow) also slaps a 30+% recharge penalty on nearby foes, and that translates into fewer attacks levied, and less damage taken by the Icer. I'm sure there's a way to mathematically quantify that, but I have no idea how. Energy Absorption not only fills up your stamina, it drains the foes, and gives you Defense for every foe hit. Again, that's not something that's going to show up well in a hero planner, but considering how you're right in the middle of everything as a Tank, there's every possibility you're going to be pulling 10 or more % DEF when you fire off EA. If you fire off EA twice in a battle you've AoE drained all the end out of almost everything below an Elite Boss, another difficult thing to figure into a measure of effectiveness.
I've pretty much only played Ice, so I'm not in a good place to compare with other sets. I think of Ice as being kind of non-traditional in how it approaches tanking, and wanted to express that.