I am Sharing Two Thing one is good and second is bad for my website

Good is
We redesigned our web development company website in Core Php. Overall, it's a great improvement in look and usability and accessibility. Also, we are ranking for some relevant search terms in organic channel Seo

The Bad is
Organic search have consistently been down 5-10 % each and every month. I am trying to dig in and figure out why this is happening, and I'm at a loss. We are aggressively publishing to our blog 3 days a week and I've built many keyword-focused landing pages.

1) I have a lot of files restricted by robots.txt - 20 of them. Many have to be that way by design because they are nodes generated by web forms.

2) We have duplicate title tags on 8 pages.
3) We have 10 duplicate Meta descriptions.
4) We have 32 html validation errors
5) We have 10 title length problems.

My question is could these errors be THAT significantly impacting our rankings?

I should note that according to Google Analytics, Referral traffic & direct traffic is also month since the redesign. I don't understand the Referral part especially, since we took great pains to put in many 301 redirects. There are no 404s or non-index able pages showing up in Webmaster Tools either.

If anyone has any suggestions for problem. Please let me know. Your thoughts are appreciated.

Thanks in advances
joyotto