This may just be a bug or maybe I misunderstood its intended design, but after playing around in some heroics last night and on the training dummy I noticed my Combustion was not consuming my DoTs. Instead, It effectively doubled their damage and lessened their duration. Is this intended or a "new patch" bug that will be fixed later (along with all our glyphs hopefully)?
Here is the spell...
http://db.mmo-champion.com/s/11129/