If it was installed with a full length liner (insulated liner would be better) and a block off plate AT LEAST in the bottom of the chimney (bottom and top is the best), then that thing would be roasting you out.
The issue you had was installation error. Not installed per manufacturer's instructions, and probably not up to code either.
These newer stoves and inserts are a completely different breed from the older non efficient smoke dragons and need to be installed properly to run correctly and get the effeciency out of them.
I'm sorry you did not give it more of a chance to get it installed properly. It would have saved you lots of work and wood in the future. KD