I think there is a waste of skills going on if an artist is capable
I second that..
around here many studios separate the 3D and the 2D, as far I know..
the CG department usually with a couple of seats for CG compositors...and another 2d dep for the flame and editor...
freelancing dependes how you present your work and then the studio put you a label...2d/3d...
but if the studios dont take advantage of a multidisciplinary artist , you can always work on role/project basis..
but I think in smaller studios you can play diferent roles...
or a specific role in diferent studios
but for sure bigger studios get more separate..
2d comp> online/desktop , roto , td , film/tv
I would say 2 skills for prod is the best , comp/matchmover comp/mattepain comp/editor comp/lighter
and more long contracts if are close each other in the pipeline...
I take a look to the job forums more studios are looking for Hybrid desktop compositors (ej Nuke/Maya)
and make sense since the comper can jump the to the 3d dep and bring the assets to 2d world is very usefull.
and I think as a VFX artist you should be able to pull a shoot from scratch to delivery , whatever you need to do to sell the shoot.
thats my thoughts..