i found a stunning little gem that works for my cards and quite a few others too.

If you ever watch you memclock drop down to 150 when mining x11/x13 then this will help you increase your GPU's hashrate.

go grab MSI AfterBurner to start off with and then open up the settings.
look down to where it says unofficial overclocking mode and set that to "without powerplay support". allow MSI AB to restart and then run your miner.

your hashrate will be higher than it was before!

I have also noticed that i can now run at higher intensities producing more hash without it falling over.
Have had a report from someone stating this allowed them to get their memclock to 1500 stable where they couldn't before.

I hope that this helps people to get the most out of their cards!

Phate

edit: starscream found this solution before I did, i was unaware of this.