I don't think that one player "hogging" all the assists is really a problem. I'm sure it would be extremely rare for one player to get even half a team's assists. But even still, I don't see why you'd be opposed to having the best passers make the most passes. Do you feel that way about other things as well? Should teams spread out their scoring instead of letting a few players "hog" all the shots? How about rebounding?
It's worth pointing out that assists are a good thing because assisted scoring attempts (shots) are generally more successful than unassisted shots. I mention this because the Celtics are getting assists on half of their made baskets this year. There are some bad teams this year so there are 2 teams with a lower percentage of their baskets assisted. Beyond that, there were only 4 teams in the last 10 years with a smaller percentage of their baskets assisted than what we have now.
A team that has a smaller percentage of it's made baskets assisted than about 98% of the teams in the last 10 years getting back a player who's led the league in assists the last 2 seasons seems like a match made in heaven, yet you seem to be concerned that the player will be "hogging" the assists. That seems like a "cut off your nose to spite your face" way of looking at things.
Actually yes, I do feel it is better to have balanced scoring, rebounding, defense, you name it over a unbalanced distribution. Remember, the Celtics got more team assists in 2012-2013 and 2011-2012 when Rondo was out for extended period due to injury. This covers the period where he set the record for most double figure assists or whatever it was.
If you look at assists/48, in 10-11 we got 6.6 fewer assists with Rondo on the bench, 8.4 fewer in the playoffs, 4.8 fewer in the 11-12 season, 5.3 fewer in the 12 playoffs and 2 fewer in the 12-13 season. It's not true that we got more assists in 11-12 when Rondo was out for extended games due to injury. It's not true that we got more assists in 12-13 after Rondo's knee injury. When he left the lineup we were averaging 23 apg, when the season ended we were averaging 22.3. That's about 1.5 fewer apg without Rondo.
For example, San Antonio, Parker averages about 6 assists for his career, Ginobili averages 4 assist. I think it is better to have 2 good passers sharing the assists vs. just one guy getting 10 assists. Balance is harder to defend. Same for scoring. Parker averages (career) 17 points, Ginobili 15 points. That is better than one guy getting 25 and the other getting 8.
Parker isn't a particularly good distributor. That's not the best example. What about teams with point guards like Magic, Isiah, Stockton, Nash or Paul? Would all of those teams be better off if those players got fewer assists?
Rondo gets assists because he has great court awareness and is a great passer. He also gets assists because he often chooses not to shoot or because he holds the ball. A more balanced Rondo would be better for the team overall. Rondo needs to move the ball more rather than trying to always hold for the perfect pass. He needs a more reliable shot so he will be more confident to shoot when there is a shot. He also needs to keep doing all of the many good things that he can do. That is how Rondo will make the team better (vs. piling up gaudy stats).
"hold for the perfect pass" = "try and create a good scoring opportunity for someone on the team". But beyond that, Rondo does have a fairly reliable jumper and does take that shot. He doesn't take a lot of threes but the number of jumpers he takes is probably close to league average. But whether that makes the team better is debatable. We score more efficiently when he piles up gaudy stats than we do when he takes those outside shots, even if he hits them reliably. Taking more inefficient shots and fewer efficient shots isn't really the best way to make a team better.