On CiviCRM 4.7.8/Joomla 3.5.1, I've experimented with variety and can't seem to get this to work. The preset reserved rules, import, inclusive in contact record and main dedupe rules are all working. If I create a new General Rule with just Email set for 10 characters with a weight of 10 and a Threshold of 10 on a group of 10, 50 and 100 contacts in a group with both known and no dupes. Running this rule just runs and runs without any results whether or not the frontend times out to 500 error.
The default Reserved Rules run lickety-split. Please advise.