It will help, but depending on what's in the organic part of the mix you could put perlite in at 50% and still find it was going anaerobic at the bottom of the pot, particularly with the new peat-free mixes. The best way I've heard it explained is that if you took a bucket of Angel Delight (like American "pudding"), how much grit would you need to add before it drained properly? A lot of these newer retail mixes just wet out into a slurry with zero structure to it. Making a free-draining mix is actually a huge challenge.