If a companion dies during the battle, it will need to be resurrected before it can participate in another encounter or be summoned as a traveling companion. Get that pet a medic! Or in this case, a Stable Master. Stable Master NPCs can heal and revive your pets for a small fee, and there is no cooldown on the Stable Master's heal. You’ll find Stable Masters in major towns and cities across Azeroth.

Keep in mind that these quests are optional, and are not necessary to continue leveling and capturing companions. They are also account-wide, so if you complete the quest chain on one character, you will not be able to complete it again on another. However, any progress that you've made will be saved and you can pick up where you left off in the quest chain on another character. The dailies that you've unlocked will also be accessible by all your toons.

5. Spending time actually leisurely talking with others once in a while is actually good for your sanity. If the only entity you're ever communicating with for days to weeks at a time is the demon soul inside of you, it might be hard not to start losing touch and eventually your marbles, especially if your inner demon is especially manipulative (nathrezim, shivarra, succubus, etc) and does more than just constantly offer you MOARPOWAH. However, you might be terrified of actually getting attached to anyone, you don't want the Legion to use that against you. Random, fleeting encounters with complete strangers in taverns and the like is the middle ground you need, to see all of these people and (well hopefully, depends on the crowd) remember what you're trying to protect in the first place, to maybe see children shopping with mama in the market place, or to hear some soldier in the bar talking about his old man back home.
26 ADP, The Fall of the Black Temple: most of the demon hunters are dispatched to Marduun, leaving behind very few, including Vandel. Vandel fights with Maeiv, trying to appeal to her reason and is left for dead. In the end, Illidan is defeated as we see in the Black Temple, and in the wake of Illidan’s defeat, Vandel hears his voice call out to him, urging him to be prepared.
In the wake of clawing, gouging, or cutting out their own eyes, the demon hunter undergoes a change and begins to see the world anew. Rather than perceiving the world as a normal individual would, they begin to understand the world as a level of energy, viewing everything around them with a fel-touched sense of sight that, “can see to the end of the universe,” as was stated by Illidan Stormrage himself to Vandel. This sight has no issue in distinguishing inorganic matter, organic matter, and even the type of magic being utilized or welling within a particular individual. A fledgling demon hunter without the proper guidance might stumble around for months or longer trying to figure out how to see in the wake of their loss of eyes, while those who were trained under the guiding hand of the Illidari might have been given an easier time coping with this newfound sixth sense due to being around so many of their comrades and those who had also walked the path before them.

I have tried it a few times. It's good if you're new to the game. Otherwise not so much. I found I leveled slower by using it, as it's suggesting to take the longest possible route usually. Basically following roads everytime, when you could take an easy shortcut. Especially if the shortcut involves a bit of fall damage, it's out of question. The "go here" spots don't also update if you take a shortcut, and then the waypoint arrow points to wrong direction. But perhaps it has been updated since then.
The most important thing you should note is that there are no official beta keys. Blizzard opens the gates to their betas by granting access to your account — not sending you a beta key. If you’re in the beta, you’ll be able to download and play the WoW Classic client from your Battle.net launcher. If not, you aren’t in the beta. It’s easy to be tricked into thinking you’ll get a beta key from an email that looks like it’s from an official Blizzard address, but don’t believe their lies — they’re all fake.
Succubus: In the same vein as the imp avoids harm, the succubus is known for slipping in and out of sight on the battlefields, attacking when least expected, and relishing in the pain delivered to their opponents. In the same vein, both pain and pleasure enact a power to the succubus. To the demon hunter bound to a succubus, this might showcase itself with a particular knack for invisibility spells, turning pain into power, and even an affinity with the use of charm spells.