You have touched upon a bit of a shortcoming in WordPress, IMHO.
However, WordPress will generate a title for the blog page out of the box --I am assuming you mean the blog index page, the list of posts-- so if you aren't seeing that title something is messing it up. Switch off you plugins and switch themes to try to isolate what is stripping that title.
That doesn't get your 'meta' tags though. For that you have a few choices: 1) edit your theme's header.php to add the meta tags, 2) hook into
wp_head, or 3) a plugin. I haven't been happy with any of the plugins I've looked into, so I am basically rolling my own class for that right now but it is far from complete.
Guessing since I don't know how your Platinum SEO plugin works...
One thing you might try is creating a page and set Settings->Reading->Posts Page so that the index points to the page you created. If you add content to that page maybe your plugin will pick it up as a meta description and/or use it to generate keywords.
add_post_type_support('page','excerpt'); to your theme's functions.php and you should have excerpts for your pages, which might also help.