Use Sidebery in Firefox for vertical tabs and it has not only better grouping but also entire "tab spaces" (workspaces) which you can switch between as well, if wanted.
I've been trying Sidebery since about 2 minutes after I made my last comment, and I think I like Sidebery more--and I've been using Tree Style Tab for _years_
Sidebery responds noticeably faster, and the panels are a great feature.