I thought I should report this as I think it's plain wrong to not have anything in GL report an error when doing this.
So I have a multisampled texture with Samples = 8 of a GL_RG32UI texture that I'm blitting to a samples = 1 RG32UI texture, and it seems to "work" however the results are far from accurate. I was really wondering what is wrong here when I tested the exact same thing on DirectX11 with my R9 280X 14.12 drivers and I get :
ID3D11DeviceContext::ResolveSubresource: The Format (0x11, R32G32_UINT) is never able to resolve multisampled resources.
So basically resolving integer formats is not implicitly supported as of D3D 11.2. Since I do have the GL_ARB_debug_output enabled I was expecting to get an error when trying to do this.