Yes, and he's also led the league in assists and restored his reputation as one of the preeminent rebounding/triple double guards in the NBA.
What Rondo does well he does so well it marks him as the designated weak defender (maybe, I still want to see him with a new coach) who's worth it. We can maybe find a better defensive PG, although few enough PGs aren't bad on that end. But we will be giving away enormous swaths of ground in other areas and threatening to return right back tot eh bottom of the league in assists.
People always talk rather vaguely about o we want a better defender, or oh in some fantasy scenario we are going to get a two way star, but that's not reality. Reality is that its possible to get a better defender. But given how few actually good, impact defending PGs there are, its not likely you are going to get one much past solid defensively. And its damn near guaranteed that for that honor you are going to lose a crapload of creativity, experience, and boardwork.
Throw in the fact that Boogie likes Rondo a lot, and that those two guys are effectively the leaders, with DC reemerging as a bench leader late in the season, and there is an obvious core to keep rather than ripping open unnecessary holes to go chase a pipedream. Upgrade the 2 and 3 defensively, start Boogie and a more experienced Willie, get a coach who emphasizes defense, do all that and a sloppy man defender at the PG is no longer any great disaster.