Not that I've used the product before, but you could always check out Video Copilot's Heat Distortion plugin? Or simply use a displacement effect on the edges of your saber effect. That would get you the main edge distortion. I'd also chuck on a particle generator that emits from, well obviously the emitter of the saber. I haven't attempted it yet, but that's how I start out experimenting. Short of 2D effects, you could always try using some particle engine to generate the whole effect. Maybe even ask on some Nuke forums if you have access to the Nuke software.