I really like the concept of the Surly Extra Terrestrial, but they are useless for heavily loaded touring because they wear out too quick and there are some QC with the moulding processes in that soft casing rubber sometimes fills the tread blocks..
I'm currently trialing Schwalbe Moto-X, but in a twist and a first for me with Schwalbe, one of them has a moulding issue too, with a deformed casing, so I'm waiting on that to be resolved.
My 26" dream tyre would be something like a 2.5 x 26" with a large volume casing, tubeless, a Kevlar protection belt to stop cuts propagating, no thick puncture guard to decrease weight and rolling resistance (relying on the tubeless to fix thorn and nail punctures) and a tread in between the ET and the Moto-X, maybe a closer spaced centre tread from the Moto-X with open side blocks from the ET.