Honestly, its really difficult to get a good live sound from an SLR. Ill always try and get a feed from the desk/use an external recorder at front of house. If a cameras static, and at the back of the venue its not too bad, but moving about the sound will always change. Ive not used the Rode Stereo Videomic, but i reckon that would be quite good for live audio situations.
For on camera sound, because I use 5D’s, I can set the audio level manually to as quiet as possible, so ill generally use that to sync with my external recorder (A Zoom H4N)