Hello all,
EDIT - Disregard gear - scales to 1000 ilvl.
EDIT2 - This is what worked well for me, and what would work for you. If you want to change anything in a route to get an extra chest, by all means. Part of the fun is finding out the best way for you.
I figured I'd write up a quick guide on Chromie so everyone else can learn from some of the things that I had to find out. I'll simply go through the steps I took in order to complete the Chromie scenario 8/8 under the 15 minutes. Note - I'm lazy, so this could be a lot more in-depth but should get the jist across.
First, I'm not insanely geared - I'm a super-casual 904 WW with poorly itemized stats. We all know how bad WW is, so this should be easier for other classes, especially melee.
0 - Sands of Time
Sands of Time rewards should be taken as a priority. Ultimately, I went through the following priority:
1.) Time-Lost Keepsake Box
2.) Bronze Dragon
3.) 30 Second Time
4.) Damage Increase
5.) 10 Second Time
5.) Damage Taken Decrease
6.) Speed
7.) All Else
1 - Clear all Bosses/Portals
In order to unlock everything, you need to clear all dragonshire bosses and portals. I found I couldn't get a clear item for each individual boss/scenario unless I had beat it prior. Rather than give a ton of info here, I think it's important for everyone to learn each scenario as it will make your decision making for speed much easier later on. I'd suggest doing the following:
Dragonshire
1.) Obsidian - Run to the end of the tunnel, kill boss. Collect Item. Kill boss when you come back outside of the caves immediately to your left.
2.) Ruby - Kill the 3 lich bosses on the edges of the crater. Once you've killed them, you can then kill the final Lich Boss in the bottom of the tree.
3.) Purple - I'm calling it purple. Go around and kill mobs below, collecting 50 of the item. Once you've done that, you can kill the boss on the platform above
4.) Emerald - Go around and kill all mobs. Each time you get the numbers required, you can kill mobs near each tree giant (there are 3). Once you've done this, you can kill the boss by the dragon palm.
Also, once you have killed each of these and turned in the quests - you can just directly kill each boss instead of doing the entire collection process.
Portals
5.) Hyjal - When you go through the portal, run immediately to your ahead and left. There will be a series of mobs that spawn near the wall - ending in the Molten Giant.
6.) Well of Eternity - Chromie sucks here. You're supposed to "follow" her but she follows you. Chromie will aggro from behind so make sure you kill anything behind you otherwise Chromie wont follow. I go immediately forward to the well, then hug the right wall the entire way following the path to the portal. Once through the portal, take an immediate left. It's fairly linear from here. Kill the end boss and continue up the stairs and down the path to find the portal.
7.) Stratholme - Do the quests - follow the paths. This one is a pain, and long. The one suggestion I have - learn where all the vendors are so when you're out doing your first quest you can buy ALL of the items required for all of the quests. This will save some time running back and forth.
8.) Andorhal - This one is probably the most gear dependent as the bosses hit pretty hard. When you get the quest from Chromie - go beyond the cannon and kill the mini bosses from right to left. You need 3 green quest items in order to do any significant damage to the cannon. Once you get the 3, you can proceed to the cannon.
2 - Pathing Strategy
Ultimately, I found out there are 2 different paths to take to kill the 4 dragonshrine. There's an easy way I found in order to tell which path you should take.
Go to the platform at this location. If there is a chest here.. you're taking route 1. If there isn't a chest here, you're taking route 2.
There is also a rare I suggest killing. He's quick, easy, and drops generally 2x Sands of Time.
Anyways, the paths. If there is the chest shown above, you take the following path.
1st Route
If there ISN'T a chest described above, you take the 2nd route. This one means that there are 3 chests inside the Obsidian cave. It takes about a minute to get in and clear them (after you have killed the Obsidian boss), and you generally get 6x Sands of Time. Certainly worth the time investment.
2nd Route
3 - Portal Routes
These are pretty self explanatory. However, I'd use the following order.
1.) Hyjal - Fastest and Easiest
2.) Well of Eternity - Second Fastest, and Easy
3.) Stratholme - Takes time but low DPS requirement
4.) Andorhal - Needs the most DPS and damage reduction boosts.
Honestly, 3 and 4 are interchangeable as you really need a skip item from at least one of them.
4 - RNG
You need to hopefully get some Time-Lost Keepsake Box in order to complete on time with current gear levels. Ultimately from this you need a couple of things.
1.) Stratholme Key - this is almost mandatory to complete on time, unless you're an extremely fast class (thinking druid possibly). This allows you to skip and go through the gate immediately on the left instead of doing all the quests. This saves you at least 5 minutes.
2.) Andorhal Documents - this is almost as mandatory to complete on time. The combination of this and they key is the only sure fire way to finish on time. You can finish on time by just getting the key, but you need to have a significant amount of DPS.
3.) Well of Etenrity Skip - Tyrande's Moonstone helps you skip all of Hyjal to the last boss. This is nice to have, but not mandatory.
4.) Hyjal Beacon - This one allows you to get directly to the last boss at Hyjal. Honestly the least effective as if you have decent DPS you can do this one in 2 minutes anyways.
The biggest thing is - Stratholme Key is nearly mandatory - and the combination of Key + Andorhal Documents is needed for most. If you dont get these by the time you're to portals, I would just reset.
One thing I'll add about Sands of Time. NEVER open one if you're in a portal and you just completed a portal boss. You can get the same one. For example, I had Well of Eternity. I killed the final boss, open sands of time, and got Tyrande's Moonstone. Wait until you're back to Wyrmrest before you open it. Same goes with Sands of Time before you kill the boss at that location. You could get the three obsidian chests, open them, and get a Bronze Dragon to wipe out Obsidian boss - when you're already there. Wait to use them until after you've kill the boss at that Dragonshrine location.
In conclusion - if you follow these VERY broad steps, and be willing to reset off RNG, you'll complete Chromie in current NH Heroic gear levels fairly easily. Don't get frustrated if you dont get RNG, just reset and go to the next attempt. Any questions, feel free to ask.
All Images: http://imgur.com/a/IFfq8