[BUG] UI Sprites really distorted when having MipMaps in packed atlas

Hi,

since 4.6.3 broke our project (partly, something with il2cpp) I thought I'd take this as an indication to try Unity 5 with our project.

Unfortunately the UI is heavily distorted when in Game Mode.

Here are some examples what it should (roughly) look like [plain screenshots taken in editor preview]:


What it looks like in game mode:


I noticed that this has something to do with MipMaps activated on the sprites. When I deactivate the mipmaps it looks "normal", but - at least talking about 4.6 behavior - we want the mipmaps, because we need to support many many screen sizes and mipmaps gave the best look for our setup.

Is this a known issue? Any workaround? Like said in 4.6 it works perfectly, but in Unity 5 not...

EDIT:
Just tried leaving out the packing tag - also works (instead of turning of mipmaps). But still this is not the desired behavior?

Regards,
Bennet