According to the ScoreHero Top 100 Rock Band Bass FCs, this is ranked #23 overall, being the highest ranked DLC song on the list and the second highest ranked non-RBN song (Visions is #14). And believe me, this song is WELL deserving of that rank.
That really fast drum beat you're hearing in the back? You'll be strumming twice as fast as the drum beat! I don't know how fast exactly the strumming is, but I'd estimate it's somewhere between 13-17 NPS. You need to be an absolute master at fast strumming, or you will have no chance to GS or even 5S this. It's actually not that hard to pass, but only because if you spam the strum bar so much with no sense of pattern you'll likely hit the vast majority of the notes in the fast strumming clusters (That should tell you how fast it is). This song on bass is up there with Nevermore (Morbid Angel RBN song, not the RB4 song) and Cimmerman Shamballa on guitar as the most difficult strumming songs on Rock Band.
I do recommend this song because it is a big challenge and it gets easier and more fun towered the end, but I have a few warnings about buying this song on bass. First, DO NOT buy this song on Rock Band 2, because then it will be impossible to FC and virtually impossible to GS due to the strumming limit. Also, by grinding this song, you may put your strumbar at risk of breaking. I am not exaggerating either of those warnings, I am actually being dead serious. Have fun and good luck!