House is what was left in the perfect point guard bottle after Rondo was poured out.
Marbury (and Cassell before him) was supposed to be a more balanced player, somewhere in the range of passable to good with his jumper and capable of putting it on the floor and creating when the other playmakers were out or needed a breather. Instead he was terrible shooter and that ruined the rest of his game. While he was a willing ball-mover and defender, his playmaking ability was also non-existent as teams simply ran under screens and let him think about bricking pull-up 20 footers or pass it around the perimeter.
But the idea that bringing in Marbury or Cassell was unnecessary and based an insignificant need is false. We have a shortage of primary playmakers. The Big 3 are still very good, but other than Paul, they are secondary playmakers. KG's post touches are few and far between and he primarily acts as facilitator and finisher on offense. Unless Ray is hot, he's not ideal as the first point of attack. The high screens they run for him against set defenses usually produce his own shot or a pass out to the perimeter that only Rondo and Pierce are dangerous enough to really make something out of. Even Paul is no longer an ideal playmaker, as his assist-to-turnover rate attests to. As for the rest of the team, not much. Perk has not developed into the kind of player who can pass effectively from a post-up opportunity. Neither has Powe. Baby should not be counted on to create. Scal, no. Tony Allen will create for the other team as often as not. Rondo is the only consistently effective playmaker on the team.
Taking this into consideration, I think its understandable why Doc and Ainge have been dissatisfied with House at the 1. You would think that the replacement for the only consistent playmaker has to bring some playmaking to the table. House brings none. What he does do is increase the efficiency of others' playmaking. But since the primary playmaking role really doesn't suit any of the Big 3, his effect is marginal when acting as a floor-spacer for a lot of iso action. That's why he shines when matched with a true playmaker, as he is able to play off another's strength and not simply shore up another's weakness. Of course these line-ups rarely work, as guys like Marbury and Rondo aren't big enough to guard 2s.
Still neither Marbury or any other available options are really good enough to dramatically outproduce even the marginal contributions of House at the 1, at least to the level needed to justify the added expense.
Given our financial limitations, it's probably not realistic to add a primary playmaker into the rotation (though Jason Kidd is a nice pipe-dream). Thus, it's probably best to enhance the floor-spacing strategy that Doc uses to improve the Big 3's playmaking. Thus, the roles to upgrade are the shooting big men (Baby and Mikki can't hack it as Posey and PJ replacements). A line-up made to space the floor for the Big 3 to operate would be a lot more effective if Perk and Baby were not a necessary part of it.
