I have been using Logentries addon with Heroku (https://addons.heroku.com/logentries https://addons.heroku.com/logentries) and it does all the things you mentio

I have been using Logentries addon with Heroku (https://addons.heroku.com/logentries https://addons.heroku.com/logentries) and it does all the things you mentioned namely, Real-time or very-near-real-time data discovery. Wildcard search. Timespan dragging. I would still like to explore splunk as an offline analysis tool for syslog drains.