Well i aint no nba coach but you can't let a 8th seed team take you to the 7th game that way.
So to answer your question and once again i aint no coach but i would have had run the offense through kg on top of the key and rondo set screens to free up pierce or allen around the middle of the key. You could have also do something basic like let rondo drive and pass (but genius doc thought pierce was the pg in that series)
This year it is different(mainly rondo gets to be a pg and not pierce). Out of all the matchup in the floor , rondo should be able to torture bibby the most. Because guys like johnson and marvin williams are actually defenders that can keep up with pierce and allen one on one well, best rondo drives and gives it to one of our big guys. Once kg or perk score in bunches then williams or johnson have to start partially doubling them which then opens up allen/pierce to drive or shoot.
To stop atlantas offense kg and perk need to be deeper towards the basket. Horford nor smith are good at shooting but like to drive for layups on bounce passes(especially smith). Gotto make them jump shooters. Ray allen who after keeping up with hamilton/kobe last years playoffs, is such a better defender now, pierce and rondo should play man to man defense and not double team. All three of them(williams, johnson, bibby) can shoot the lightsout otherwise
It will be a close game and even though the celtics motto is to live and die with defense, putting a bit more effort on offense will be a higher key to win