..erm.. in one word..
No.
To extend, for the first two albums the bass was very good as it didn't merely copy the guitar parts and was reknowned for always going off on it's own melodic 'adventures'.
MAYH's bass was linear..so i'll give you that.. But that's merely because Mikael did it.
But Martin Lopez's basslines are generally not that linear, and i feel he is definitely one of the most impressive bassists within the metal scene. He keeps the repetition of guitar parts to a minimum, and frequently uses short bassline fills.
So.. although at times it can be at times, generally Opeth basslines are non linear.