The guy in the picture holding his third place trophy in the IBO Trad World is the one who I dropped his bow poundage 4 times for. He shot the reworked bow in last weeks championship.
My point is, a properly done poundage drop will not hurt a bow, and yes I put the bow on a tree and go through the entire tillering process like I would on a new bow as I drop poundage.
Of course, if you are trying to drop poundage on a poorly made, hingy bow, you are probably wasting your time. You will still have a hingy bow, just of lower poundage, bad hinges can't be fixed.