I meant on the road they are dogs. I tried them all and it was the least road friendly diesel. The Navaras (the 2.5L) are underpowered but drive like a car, the old BT-50 had heaps more pull. As a road car the D4D falls way short of the V6 Hilux, but it too has its downfalls: it suffers from lack of sub 2000rpm torque and this makes it bad as a manual, but this is basically a non issue with the auto. The D4D 3.0L goes OK, but it is too small for a 2 tonne vehicle.
I agree with you that a bigger diesel AND a V8 would fix the niche. A 4.0L (even a V6) Turbo diesel or a 5L+ long stroke V8 in a Hilux sized vehicle would be great (something like the bore/stroke of a 307 SBC). I don't have an issue with the Hilux as it is as a road vehicle and an occasional tower. It is strong enough for that, and I rarely go off road. I don't think any of them should be rated higher than 2.5 tonnes tow capacity.