The current version available through Nuget doesn't support intercepting ExtJS ajax calls. It seems that there is a pull request for that feature, but it isn't available yet.
Here's what I had to do to get around that:
Ext.require('Ext.Ajax');
Ext.onReady(function () {
Ext.Ajax.on('requestcomplete', function (e, xhr, settings) {
if (typeof (MiniProfiler) != 'undefined') {
var stringIds = xhr.getResponseHeader('X-MiniProfiler-Ids');
if (stringIds) {
var ids = typeof JSON != 'undefined' ? JSON.parse(stringIds) : eval(stringIds);
MiniProfiler.fetchResultsExposed(ids);
}
}
});
});