Bmibaby www.bmibaby.com operate this route a couple of times a week. However, be careful as Lufthansa are taking over BMI and may sell-off Bmibaby.
Then as you mentioned there is Ruinair.
It is possible that jet2.com may step in. They operate from EMA to Greek and Turkish Destinations. At present, they only operate from Leeds Bradford and Manchester to Faro.
Thomsonfly operate Doncaster - Faro weekly except between November and March. See: http://flights.thomson.co.uk/thomson/en-GB/timetable/findbyroute?departure=DSA&destination=FAO
See this article here:
http://www.thisisleicestershire.co.uk/news/Airline-easyJet-axe-jobs-East-Midlands-Airport/article-1311325-detail/article.html
