Small dozers have kinda a limited area of use, now with that said so do big dozers. Sales numbers on small dozers have always been higher than big machines, what you are seeing is a trend for the mid sized machines edging into the small market with the advancement of grade control, give the manufacturers time, the grade control will be brought into the smaller machines.
I have a TD-12C for the work I do it is a ideal machine, for the most part... but sometimes it is like killing a fly with a shotgun... I really like the machine, I was on a job and the guy working next to me brought in a new D-6K and told me I needed to run it, so I spent some quality time on it, nice machine, but I like my 12 better, I would love to have the cab though. ...
It is a shame that Dresser has never been giving the chance to thrive, Komatsu basically killed them off.