The requirement for a steep approach on RW 28 was the need to clear the planned new bridge - the East London River Crossing; this has not been built.
The bridge is winding its way through the planning process. Expect construction to start in a few years.
Here are links to show its location and the appearence of what you will be flying over. Note the approach to 28 does not pass directly over the high point of the bridge mid-river but over the south shore approach.
Map :
http://www.tfl.gov.uk/tfl/downloads/...ntmap-0408.pdf
Picture:
http://www.tfl.gov.uk/tfl/thames-gat...gb-about.shtml