Perhaps someone at Blizzard can pick this up and pass it around, just in case some of the current talent moves on to bigger and better things.
Note how lots of these things bring value to an organized encounter, but collectively bring only misery to the world of random matchmaking.
Place Lots of Trash That Drops Nothing and Gives You Nothing
Organized modes have trash that gives you reputation and the occasional epic or even toy. Let's not have that in LFR. By "that" I mean the reward. But leave the trash there to slog through.
Place Lots of Optional Trash
Optional trash opens up a world of possibilities for random parties. Perhaps they can all sneak through it using exactly the same route. Perhaps they won't.
Place Optional Trash That Can Easily Be Skipped and Is Annoying If Pulled
The blind dudes that hit like trucks and take a couple minutes to kill. Sure, why not.
A room with several platoons of orcs practicing their killing skills off to the side. Sounds great.
Place Optional Trash Where There Is No Obvious Path through/around It
Imagine if you will an almost completely dark cave with three objectives in it, lots and lots and lots of trash, and several entirely reasonable routes between the three objectives, none of which is everyone's favorite.
Imagine if you will a quarry which must be crossed whose cliffsides are covered in trash, with numerous entirely reasonable routes through it, none of which is everyone's favorite.
As a bonus, this makes it much more exciting for players zoning in after the group has already wiggled its way through the mobs. "Hmm, which way should I go? Maybe I will just mount up and RIDE FAST STRAIGHT AT EVERYBODY."
Place Optional Trash Where It Can Be Just Barely Be Skipped
Let's go back to that almost dark cave, with numerous trash mobs patrolling back and forth, and 25 boisterous heroes bouncing around "trying not" to pull it.
Or, imagine a long stairway, where bones conveniently mark the locations of annoying mobs that could be skipped by simply walking around them ... or not.
Place Optional Trash Where It Can Be Pulled During a Boss Fight
Nothing livens up a fight with a hydra like a dozen cave spiders and a screaming worm made out of stone rings and a big pissed off fungus elemental thing.
The Boss's First Action Should Wipe the Group If The Group Is Out of Place
Who pulled the hydra? Dammit, I still got the mass rez debuff.
Place Trash Far, Far Away from the Entrance
DO NOT COME IN. DO NOT COME IN. STOP WALKING IN. OMG STOP STOP THE TRASH STILL HASN'T RESET.
Add NPCs That Pose Interesting and Pointless "What-Ifs"
Tyrande, I wonder, how many of these trash mobs would it take to kill her? And then what would happen? I don't suppose you 24 guys who waited an average of 30 minutes apiece to get into this instance mind if I experiment for a while do you? (We will be constantly in combat so you can't kick me, woo hoo!)
Follow a Chaotic Mess with a Super Important Action That Requires a Little Care and Coordination
After 15-20 minutes of killing multiple huge rooms full of insane orcs and goblins and machinery, everyone should have to stop at the entrance to a hallway and wait patiently while someone applies CC in the one and only one place in the entire four wings that it is more or less necessary. And then everyone should avoid spamming AoE right on top of the marks. Now, it's certainly not the hunter's first time placing a trap in a raid ... or is it ...?
Don't Fix Toys That Can Be Used for Evil; Don't Even Nerf Them
The Battle Horn is fine. It shouldn't emote "/e sounds her Battle Horn!". It shouldn't appear in the combat log. Because if it did, people would know who pulled the trash/boss/both. They would know after the first wipe, not the fifth. They wouldn't start kicking random suspects who showed up in "Who Pulled" and fail to kick the actual villain because the Battle Horn doesn't work that way.
In an Especially Long and/or Tedious to Reach Encounter, Make the Likely Failure Point at Least 10 Minutes into the Fight
So, you do need to single target the blistering tentacles.
Also, you need to attack the mind controlled people.
Make Sure that Important Mechanics are Well Hidden
I got this ... like ... Mark?
There are these purple orbs. It's really important to soak them. They're not real big though and they don't stand out in all that ... gray and purple.
And speaking of not standing out in purple:
Create Encounters Where You Have to Follow the Leader, and the Leader Has to Be Right
There is one path through the purple maze, or two paths if have good eyes and run fast. Everyone is going to follow the person with the mark, if there is a person with a mark, near the center. But often, he won't be on any path. In fact, he might not even be the tank or the "leader."
Use the Same Graphics to Mean "Come Here or Die" and "Get Away or Die"
This expansion seems to be the expansion of the group and soak, not the living bomb. I guess the living bomb was old.
Make Sure that Organized Raiders Bring Incorrect Strategies into the Group
Ah the legend of DPS OFF THE BOSS DURING DEFENSIVE!!!