I tried to update to 2.2.0-beta but the ?order[foo]=DESC does not seems to works anymore. The order is not set in the query anymore.
I bisected api-platform and the commit breaking this is 63d555a (PR #1633 )
I investigated a little and it seems that the doctrine query is OK in FilterExtension after applyToCollection method call, but is not present is symfony's debug toolbar.
If you have an idea @dunglas ?