Can you define "high usage"
Average to high usage, in my perspective, means pretty heavy screen on time, with task such as browsing, phone calls, emails, gaming and youtube videos.
If I can recall correctly I did the below things:
The usual browsing of all the Windows blogs
(~20 minutes)
Research the lenovo yoga 2 8 (~30 minutes) (awesome little device!)
15 minutes phone calls,
Sent emails
Jet car stunts gaming for 30 minutes (I love this game, reminds me of trackmania!)
One 1+ hour long documentary on Perfect Tube and a couple of 10 minutes videos from the subscription feed,
Set appointments and reminders / note taking with onenote / saved map locations
Updates / downloaded 2 new apps, tried out, deleted..
In the night browsing news, about the asteroid flyby, sports and those Windows blogs again (!)
20 minutes music playback with groove
Searched and downloaded photos with Perfect Wallpaper / Edited a bunch of photos with autodesk pixlr
Spent 20 minutes on Readit
Many calculations with the calculator in order to build the space station in kerbal (I'm a noob)
This is pretty much what I remember I did with the phone.
Of course they where short screen on sessions for minor stuff as usual
The fact is that the usage scenarios are defined exclusively by the user and everyone has different perspective on those 3 values (light,average and heavy)
I wrote average to high usage because after all the work and media consumption I've done, I wasn't expecting the battery to last that long and frankly, it is on par with WP8.1!