This only concerns coop in full, at least, as far as I'm concerned.
When viewing my stats for coop games, I think it would be much better to view each team member's stats side by side. There is a ton of empty space and needlessly large fonts taking up space on the web site (sure, it works if people are viewing from the couch on a tv, but still). In fact, the large font could stay as long as extra words were trimmed. It would be great to see all the stats for the three coop players all at once.
The weapon stats would have to be squished pretty good to make it work. However, I would prefer squished to having to click each member seperately and copy and paste to a spreadsheet for a direct comparison.
Overall I don't have a problem with the layout. The box for 'Players' in 'Match History' should resize dynamically depending on how many people played in the match. Data should be compacted and transmitted with the fewest number of clicks necessary. To me this means putting up everyone's data on one page with no extra clicking required.
Just my two cents.