Odd load balancing problem

[masterplan]

I've got my load balancer set up in using the Sunday 10th 22:00 i386 build, but the issue is with the network speed. I've got a 20Mbit, and a 10Mbit link, one is a cable connection and one is a DSL connection, the traffic is moving through the two, but when I run something which should in theory be using both links (a torrent for example) I don't get the maximum throughput I'd expect, in fact, it goes even slower than my cable link alone barely going above 2MB\s, but when I use the links separately (either or) they get 2.3MB\s and 1.1MB\s respectively.

I was wondering if anyone has come across this problem before?

To give a bit more information into my setup here is a small diagram,

And if it's any help, my config.

Thanks