Yeah, I solo stuff with my vw tanking all the time, works much better than a felguard in every other way, just gotta have the patience to wait for it to build up threat.
Threat management is key, and long term survival soloing a hard fight is much about that anyway when using a pet tank.

Soloed the raptor boss in ZG a couple weeks ago on my lock using VW to tank with demon spec.

Another important key to vw tanking threat is the demonic empowerment ability which increases its treat output.