2 Shielded tank would be my choice for aesthetic appeal and defensive style of play. Accept, unless it could regularly replace the other tank (to be a solo tank in 2-tank instances) it would probably be disregarded because this game is obsessed with DPS and is designed around it. And if it COULD properly solo tank 2-tank combat, then other tanks would be discarded.

...On the otherhand it could have absolute 0 DPS (or close to it) and consistently support the DPS members to make up for it. I'd like that because it would force DPS to be responsible for the level damage being put out rather than the healers and tanks.