If you actually watch the games, they have multiple problems and little to do with Rondo. Yes, the offense has declined, but Rondo's defense has more than offset that. They don't have constant bench production which is hurting them.
Rondo has actually played well for them but he's the new kid so an inordinate amount of attention has been placed on him. I watched a lot of Dallas prior to the trade and a lot after the trade - he's helped their defense tremendously, but they still lack a wing defender that can guard bigger 2's and 3's. Chandler Parsons is an okay defender, but they need someone stronger there. It could be Aminu off the bench, but he can't seem to keep a spot in the rotation due to his lack of offense - maybe they should abandon hope of him developing a jumpshot and put him with a big man this offseason who can show him some post moves. He's too big, athletic, and defensively aggressive to have Richard Jefferson take minutes away from him.
They're rebounding is horrid. Tyson and Rondo are frequently the only Dallas players who actively seek rebounds (Aminu does as well when he plays) but they get killed by good rebounding teams like Memphis. I can't count how many good defensive possessions they spoil because no one can secure the rebound. Their best hope for improvement in season is Chandler Parsons stepping up his rebounding game.
Good post! Rondo is not their problem. They should stop their addiction to a wonderful and pretty offense and trade Parsons for some quality physicality. There are teams out there with good physical 3's and 4's to spare who could use Parson's offense. Too bad Monroe is not easily traded because Detroit could trade him and filler for Parsons and get back a little something extra from Dallas (Ledo?)
Toronto has and abundance (James Johnson, Terrence Ross and X for Parsons).....(Patrick Patterson and Landry Fields for Parsons?).....(Parsons to LA for Jordan Hill, Wes. Johnson and Nick Young?)
EDIT: Another trade, with Portland:
Parsons, Aminu and Charlie V. for Dorell Wright, Kaman, T. Robinson, C. McCollum and Portland's first round pick. Not sure if the Blazers can afford that for next year though...