Mythic+ Tips and Tricks
What Do You Need?
Cooldowns that are greater than 3 minutes will reset on dungeon start. On top of this, many of the buffs themselves that are applied from these 3 minute cooldowns do not get wiped on key start (except Bloodlust). This means that there are many buffs from things class related, conduit related, and dungeon related that you can keep for a few moments during the first pull of a dungeon. This makes big pulls at the beginning of instances such as Halls of Atonement and De Other Side much easier.
How to Pre-Buff Before Dungeons
As I said, these buffs are on a per buff basis, and a lot of cooldowns in the game do not remain or reset on dungeon start meaning that you will not have your major CD for the first pull of the dungeon. If I do not have your cooldown or buff listed, that does not mean it explicitly does not work and I may have overlooked it.
Class Related Cooldowns
For as long as I can remember, there have been a couple of classes and a couple of cooldowns that are pretty valuable to use prior to the key inserting. The ones that allow you to maintain the buff and are useful in some manner are:
These buffs in varying degrees of usefulness depending on the dungeon and the first pull of the dungeon itself.
Refined Palate can be used by everybody in the Theotar tree to get an extra long potion at the beginning of a dungeon. Some people even will use Theotar as the countdown is going for your dungeon, pop your potion, and swap to a different soulbind in order to maintain the potion buff as well.
Wasteland Propriety works for Venthyr Paladins with Ashen Hallow. The long cooldown on Ashen Hallow makes the Tea Time buff granted by Wasteland Propriety very long. Your paladin just needs to use Ashen Hallow the moment before the key starts and the whole team will have the versatility buff for an extended period of time.
Inscrutable Quantum Device when used under the effects of Bloodlust lasts 25 seconds. Both IQD and Bloodlust reset when the key is activated, so you can have access to 15s of the IQD buff after the gates drop.
When to Do This in Mythic+ Keys
All of these tactics are practical in weekly keys and normal runs. Feel free to implement them as you see fit and if I missed anything feel free to use it at your discretion :).