A little knowledge is a dangerous thing.
The aim of SEO is to get visibility,
The aim of visibility is to get traffic (clicks)
The aim of traffic is to convert into the required action (sales, sign ups etc)
SO
it follows that the aim of SEO is to get action, sales, sign ups etc.
You need to know what does what at each stage and with regard the first stage, your developers are quite right, Google doesn't use the description content to rank a site, it plays no part in their algorithm. HOWEVER, it DOES look at it and will, (if it is good enough) display it underneath the blue link on the search engine result page.
So to that end, the description is very important as it encourages the clicks, which are needed to get the sales.
SEO in 30 seconds HERE WE GO
make sure you have carried out good keyphrase reasearch
Group your content into sub niches of your site theme
Apply your keyphrases to the most appropriate pages
make sure there is a home page for each sub niche and link from it to all the child pages, using the main keyphrase for the target page.
make sure all your pages link to
A. the homepage
B. the main sub niche homepage
make sure your content on each page is tight and contains the main keyphrases plus semantically related and stemmed phrases. break the phrase into individual words also
make sure that your page titles use your keyphrases for that page. most important given the most prominence etc.
Do the above and your on page SEO is half decent.
OFF PAGE:
Get links , get them from web2.0 sources if possible, don't get too hung up on nofollow dofollow, but make sure you get a decent enough buch of do follow links.
To appear natural the mix should be no and do follow.,
Vary the keyword anchor text, get some links with raw urls
www.domain.com
Get deep links to your sub niche main pages using the target phrase for that page.
Repeat at product level
If the site is new, then issue a press release. Talk to local publishers and get a listing in their site somehow, beg steal borrow etc.
Do the above and your poff page SEO is half decent. Then, come back and ask more questions