One of the major points of discussion on the Opeth board was that Axe has been in the band for going on 3 years now and he still plays machine-like, almost too machine-like for their tastes. While I certainly agree that he needs to loosen up, I'd rather him be more stiff but play consistently than loosen up and start fluctuating tempos.
I'm pretty sure that's why they ended up dropping songs like "Forest of October" from the setlist when Lopez was still in the band, because he'd fluctuate too much when playing older material and it'd end up fucking things up for the rest of the band. It's really a shame because some of the things he came up with were brilliant.