Hi,
Text > HTML ratio isn't actually a ranking factor and there is no penalty based on this. What you can do with it, is use it as an indicator on how big your pages are and identify those that might be slowing do the loading.
There is no test or correlation that would suggest that reducing this text > HTML ratio will do anything for your rankings.
You need to also try and get away from the thought process that SEO is just about search positions - you need to think about customer acquisitions and page usability as well. For example, if I look at your home page and you were to just add a block of text at the top, then this would reduce the effectiveness of the big messages and search availability at the top. it would push down the main search box and offer nothing of use that anyone would really want to read.
So no, don't add text to the top of the page as this isn't needed. If this were just one big picture with nothing at all there, then it might be a different discussion.
Are your search positions dropping at the moment, or is there a reason that this came about?
I have clients whose Text > HTML ratio is 6-8% and in 1st position for very highly sought after terms. There is a lot more at play.
-Andy