Thanks for the feedback. We are using an in-house engine and currently have no option to display alpha overdraw. The trees also transition straight to impostors, but you wouldn't be able to tell the difference as the code team have done a great job with this
The decision to go with this style of leaf cluster was so we could change the leaf clusters on any tree to give it a different look. Its very similar to older versions of speed tree handled it. Should be pretty easy to optimize these if needed (I think they will need it).
However I think I may have previously made the leaves far too small. I've rendered them again and feel they have a much better look. Also looks a lot better in substance painter which is closer to our in game look. Just looks awful in max even after applying custom normals