LucidSW - 6:53 pm on Feb 15, 2011 (gmt 0)
> Historically my CTR hasn't dropped from 2.2%, which I guess is good.
Well no, it's not good if your QS is only 4 (but you may have meant at least it's not going down). The largest component of QS is a calculation of your CTR compared to the historical average (exact match as Rhino pointed out). So you are below average. Note that position is taken into account too.
> keywords positioning on the landing page
Are your keywords showing as being relevant? If so, no need to change your landing page. You need to concentrate on improving ads to get higher click rates.