I found this is due to using the non-flash wowza player in the browser.
With force flash ("useFlash":true) poor quality streams play much, much better.
Because I have a few poor quality streams I now force flash on any browsers (the wowza player falls back to non-flash player if necessary).
I was wanting to be Flash Free, but it is not practical yet, and this player is still a step up with inline Android playback and decent vod playback (I still force flash there also - the non-flash player is more particular about formats).
And the player does provide non-flash playback in browsers if need be.