In my experience...
60% of the time PUGs will squeeze by a morrowgar kill, or just be a few hour-long wipe fest.
If a group downs Morrowgar in 1-2 attempts, LDW goes down after 3-6 attempts. Otherwise, most don't get past this this fight.
PUGs good enough to down LDW, one-shot the gunship battle (usually)
20% don't down saurfang, but PUGs that do down Saurfang usually disband after loot is distributed.