There's a few sites around like https://wows-numbers.com/ https://eu.warships.today/ and http://www.wowstats.org/ that use the WG server API to get statistical data of players and other things and display them.

This is the data that is offered:

• Overall performance of a player (frags, xp, WR, etc.)
• Overall performance of the players ships (frags, xp, WR, etc.)
• Players achievements (i.e. "medals" count such as Kraken, High Caliber etc.)
• Players Performance within a specified date window (frags, xp, WR, etc.)

There are a lot of desirable things missing in this API, such as:

• The raw sequence of data on a players battles (i.e. an array with battle results) over N battles (not dates)
• The performance of a player, a players ships and ships over the N battles, like the last 10, 100, 100 etc.
• A statistical aggregate on a players performance, players ships performance and ships performance over N battles at M granularity. For instance an array of records at a granularity of 100 battles each over 1000 battles -> 10 records.
• A sliding window average on a players performance, players ship performance and ships performance over N battles at M granularity with an X sliding window size.
• Server leaderboards sorted by different criteria
• Ship leaderboards sorted by different criteria
• Enhancement of performance data to include base xp (not modified by premium xp), achievements, ribbons, dmg received and dealt information, and so forth.

The sites which display some of the information I've listed here as missing, compile this data by themselves, from the users they know about from having been requested to fetch those players data. This is an inaccurate view of the data and suffers some drawbacks (for instance that no reliable performance graphs can be drawn and progress data display is awkward at best).

It'd be nice if WG would consider at least some of these requests for missing APIs so that better statistical information can be displayed.