Loss in pageviews after Google Sitemap submit

[isync]

I recently uploaded sitemaps on my webpages. One page got a boost of 18% in impressions, another site did not move, and a very complex site all with sitemap_index and multiple sitemaps (~200,000+) pages resulted in a huge loss in impressions.

My site has a simple layout. A database of things which you can show, and comment on. The things main "show" pages I rated with a weight of "0.9" in the XML sitemaps, the comments with "0.7". I thought this would reflect the site-layout/page importance and google would compliment me for that. But obviously didn't..

Any ideas? Should I modify the weighting? Or should I remove the sitemaps alltogether again?