Octavarium isn't their worst, and I think it's worth the price of admission for Root of All Evil and the title track (even if it's a bit overlong), which are great, and the other solid numbers (These Walls, Sacrificed Sons, Never Enough). In general they wear their influences very openly on that album- hence Never Enough sounding a hell of a lot like Muse, and the two songs mentioned above sounding a lot like an attempt to ape U2.
In my opinion, Panic Attack is by far the worst song on that album, and one of DT's worst songs period.