Increased loading time on android devices with Unity 5

You said the delay is before Awake is called. Awake should never be called with a sizable delay of any kind. Not sure what could cause that. What exactly is happening right before the Awake that takes so long?

Perhaps the Unity exporter for version 5 has been altered in a way bad for performance? Have you set up some Groups to not load until told to play? That could help some. Or are you using "file from Internet" settings?

You should also test if it behaves the same with a non additive level load and see if it's the same just to narrow things down. We dont use LoadLevelAdditive so I don't have any insight into possible Android bugs on that front.