I know it's frustrating when it happens (especially mid to late through a dungeon), but I don't think it should be punishable. Mainly because of the monthly subscription not only for XIV, but PSN as well. SE is not going to moderate something like that harshly, because that would ultimately effect their cash flow. You already get penalized for a disconnect (30 minute restriction on Duty Finder I believe)?

Most everyone has had a disconnect issue in some form or the other. There have also been times that people purposely disconnect for whatever reason (IE not happy with current party, time constraint, etc). There are a plethora of reasons why someone may do so. But punishable on a more "extreme" scale? That's a bit unnecessary, in my opinion at least.