I my very well be missing something, but bumping up the EC seems like it would be defeat the purpose of using high ISO. Typically, when I choose to increase ISO is in low-light situations when I need an increased shutter speed...however, if I increase this EC, this is going to in turn DECREASE the shutter speed again.
If you're maxed out with your standard, non expanded ISO's, then the trade off is a underexposed image that is free of camera shake induced blur, but needs to have more NR in post, which can take away detail. But as long as you can increase your ISO, that should be done along with exposing as much as you can without blowing highlights.



