Actually, I think they are.
They are going to be an extremely difficult team for the Celtics to beat in the playoffs even if Rose is only playing at 50-60%. They're that deep and that good. From a matchup standpoint, the Celtics are going to have a tough time dealing with their rebounding prowess and their team defense is superb.
They seem to thrive in some areas where the Celtics are weak. That's a big concern of mine.
That being said, the Celtics can beat them but only if they're playing at the tops of their game for 4 out of 7 games. Bulls are prone to periods of offensive stagnation and if the Celtics can capitalize in those situations, I like their chances.
Also, like Faf mentioned and I mentioned in a thread a few days ago, Deng is prone to disappearing acts. When that happens, the Bulls are a much different team and very beatable. Combine that with a beat up Rose and the Celtics are in great position if they can convert their scoring opportunites and limit Chicago's second chance scoring opportunities often brought on by their rebounding.