4 man dungeons vote kick is where it is the most important. I have experienced many instances of someone dc'ing and not returning for 10+ minutes. This is when we NEED to kick someone as some instances require 4 active persons. 8 man dungeons can at least be completed with 1 or 2 people not doing their jobs as their is another tank/healer/dps to make up for their incompetence (I know, this does not make it OK).
As far as withdraw penalties, they seem to be doing wonders for df ques. I rarely see members drop anymore. Perhaps removing the penalty from full premade parties would be more ideal, as this does not affect other players queing up. Perhaps increasing the timer to 1 minute would make things better for crafters/afk dps/gatherers/etc.