The Duty Finder NEEDS a penalty lockout debuff for leaving a group before anything else.
I've been level 50 for 6 days now and have been able to run maybe 3 level 50 instances because of Tanks and/or Healers either instantly leaving after we all get in, when someone says they are new to the instance. Or having the Tank and/or Healer leave in the MIDDLE OF A FIGHT when one person dies for the first time on a boss.
I don't mention DD because we don't leave since we have a 1 hour+ wait time.
How are people supposed to learn fights/ instances, etc... if they can never even TRY them?