No it should help everywhere, its less overhead for the GPU so it can do more actual computing and less "talking" about what its going to do.
It will take a while for these types of gains to be shown for most game engines though, as they have to be designed around that not just tacked on. So you might not see any gains with DOTA 2.
The gains are to be found in games like Dark Souls, Skyrim, Mount & Blade, Total War, Freespace 2, most MMOs (raids, guild vs guild, world vs world, etc), that sorta thing.
Good example in Skyrim; each NPC makes around 40-50 draw calls, due to all the textures used on them (body texture, scars, brows, tattoos, blood, hair, etc.). If you overlook Whiterun, you're making around 3.5k draw calls, which brings me Phenom II to a glorious 27 fps. Get rid of all the NPCs, and oh my, I'm down to ~2.8k, and I'm at a good ol' 35-40fps.
With these modern APIs, we're not talking a couple thousand draw calls being the performance barrier. We're now talking several tens of thousands of draw calls (per core!) being the limit.
If OSG gets Vulkan functionality, I'd love to see what modders do to the ol' OpenMW; an open world engine with all the objects you can throw at it. Mmm.
I'd also like to see how this affects 3d rendering. Might make the 8350 the utter king, if 3DS Max (or whatever) adds support for Vulkan/D3D 12. parallel draw calls AND parallel rendering, rather than just the latter on it's own.