Easier solution !!!
I have the same exact problem with Google Now Launcher installed on my M8 !
The weird thing is that when I am on BlinkFeed Launcher the navbar is totally transparent , but when I switch to GNL it is getting that darkish tint to it. I mean so far wherever I installed the GNL (with KitKat) the navbar was as transparent as it should be.
I just read the post by shorty1483 here and also in the ViperOneM forum and looked at the results. I should say that it's a nice solution, but as I see here from some of the responses, a bit complicated to follow.
So here is an easier solution to this problem with a similar result.
So if you are ready to modify some system data in order to achieve the desired transparent result I am assuming that you have your phone rooted (Unlocked, S-off,,,) . So then you can very well go and install the Xposed Framework and then install and activate a module called "Translucent Style", where you will have several options to choose from for your navbar, but the only options which give the desired effect are the once which have the KitKat name in it "KitKat gradient " , "KitKat gradient dark", "KitKat gradient light",, so choose one of this and you are good to go.
Note: one of the requirements for this mod is to have BusyBox installed !