I was going to vent about it with a rant, but I've decided that less rant, more suggestion may be better.
So, the problem with PUGs, at least as far has HM Z-quests goes, is not what you may think. It's not the so-called noobs, or the inexperienced players.
No, it's the experienced players who should know better that are the problem. So instead of a rant I'd like to offer these tips for PuG'ing to those semi-experienced, think-they're-leet, players who screw it up for the rest.
1. It's a PuG, this naturally means that you may get inexperienced players and/or players with skill bars that are (in your opinion) less then optimal.
2. Many missions and bounties have "back door" methods to get them done - alternate paths, enemies that can be avoided, etc. Keeping #1 in mind, not everyone in a PuG will be aware of these alternate methods.
3. Keep it simple - keeping in mind #1 and #2 - it's often simplest and fastest just to do it "oldschool". Do not assume that everyone will approach the task in the same manner as you. Be willing to learn new methods.
4. Pinging and drawing madly on the compass during the mission/quest is not helpful. No one knows who's pinging or why, or what they want, so it often just leads to the group being confused and spread out everywhere.
5. If you really, really want people to do things a particular way - explain it to the group before you start. I know it will take up some of your precious time, but...
6. If people go the "wrong way" and agro things you think you should avoid, it's much faster and easier to simply help kill the agro rather than whine about it or, worst of all, go off your own way without helping. Stay with the group.
7. Don't run way ahead of the healers and/or run past agro and then whine about not getting healed. (From the PuGs I've been a healer in.

8. Unless you actually are the leader, don't try to highjack the group and enforce your own view.
/rant
There could be more, but I could add them later. I think #3 is the most important overall.