Not to diminish the playing on the video, but the effect of the contrabassoon in those chorales in Mahler 2 should not be underestimated. It works perfectly with the tubas to provide that glorious sound. I did not realise its effect myself until I played the work and could actually feel the contrabassoon vibrations through my tuba (at that time a Besson 981 Eb!).
I remember reading an article in the TUBA Journal (now ITEA) that the harmonic profile of the contrabasson is strongest where the tuba is weakest and vis-versa, so they perfectly compliment each other. I have wondered why contrabassoons are not usually used in concert bands to support the bass part? Would seem to make good sense and be far more appropriate than string bass, or electric bass guitar!