I have yet to achieve master builder status. I have built three huts, hospital and sewing hut, repaired the love shack, cleared briar patch, cleared vines and am 90% finished on the floor- no master builders yet. Is it even possible to get there?

Yes, but you have to try not to spread them out too much, most of the building work is done now. People set to building should automatically repair huts now though, so you can get some exp there. If they don't, just drag them on top of the huts so they can work on them.

Many builders finish a job quickly; problem is the accumulation of skill is also spread among all of them - leaving you with many, many adept builders, but no masters