Wing 3 is 'the final stretch'. The two lesser wings need to be cleared before you can even enter this wing, in a similar fashion to how zoning in to Sapphiron's lair in Naxx works now. The door has a magical barrier surrounding it, with two gems to either side of the door itself.
The inner circle area where the raid first zones into the dungeon contains the two pylons from the Gatekeeper fight. These two pylons are activated at the end of each of the lower wings, and channel beams that shoot from the respective pylons to the gems on either side of the door. Once both beams are active, the door is able to be opened.
Wing 3 contains two more encounters: The Garden, and the final showdown with the Baron. The garden event is similar to Karazhan's opera, in that there's a few different options for which fight is happening per raid ID. There's the Tree, the Green Dragon, the Rock, or the Ooze. This random fight is chosen as the raid zones in, and is held in the background while the raid clears the lower wings. Once finished, and the beams from the pylons have deactivated the barrier for the final wing, the raid is swarmed with various adds as the final doors are thrown open.
If the Tree is the active fight for the week, then a swarm of treants piles out of the third tower's doorway as the doors are opened. The Dragon encounter has whelps piling out the door, the Rock has rocklings, and the Blob encounter has an army of slimes oozing out of the open door. These mobs all have abilities that reflect the upcoming fight in the garden... whelps sleep attackers when hit, the slimes have stacking poison effects, the rocks hit hard, and the treants have an effect similar to Nature's Grasp that have a percentage based chance to root attackers (melee or ranged, equally), and inflict bramble damage.
I don't see this being some huge ordeal to overcome, it's just a variable that you won't know what's going to come rushing out of the door (25 adds for a 25 man, 10 for a 10), but once you do see what it is, you know what the Garden holds in store for you that week.
Once inside the tower proper, it's a short flight of stairs to the actual Garden itself, and a quick chat with a druid before the fight begins (see here).
Once that's completed, you all ride a set of elevators up to the very top of the tower. The elevators themselves offer one final challenge before you make it to the showdown. I doubt this would go over well on the forums, but I'd really like to see some very basic platforming element come into play. Whether this is a simple 'jump across the gap from elevator number one to number 2', or something more intense like 'leap from elevator 1 that's moving quickly to elevator 2 or 3 that are moving slowly to the right and left, and then immediately onto elevator 4 before elevator 3 bursts in to flames, and 2 smashes into a wall of spikes' is up in the air. We could even throw simple bats that daze or slow into the mix for extra mayhem.
Again, I can already imagine the amount of crying this would incite on the official forums, but some of the more simple platforming elements of WoW are the ones that get people talking in vent during raids. The guy who always fails during the jump to Thaddeus, or that one guy who invariably fails at frogger after Patchwerk. The little gap in Wailing Caverns that you had to leap, or the other one in Blackfathom Deeps that, if missed, would require you to swim back around and give it another go. Heigan is a pretty simple concept, but many people dread being 'on display' for the duration of the fight if they die early on.
We could make it as crazy or simple as we like, but having it there provides one last little check before you move on to the boss. There's also a small break before entering the final area, where we have a short chat with Chromie of the Bronze Dragonflight (see the Baron fight description), so anyone that didn't make it could try again while the raid waited, or be summoned up. We could even have a failsafe elevator in place so as long as SOMEONE made it up, they could lower down the 'failevator' for the nubs. Although, were that to be the case, I would imagine that people would just afk while someone made the trip up and they all waited for the safe elevator to come down. An achievement could be implemented: "Elevator Action - Have the full raid enter the Baron's Observatory without summons or the use of the dumb waiter".
