Your cinematic has allot of work to be done to in order to get on the level of entertainment, here a short review with some pointers and ways to improve future cinematics.
General:
This is going to be constructive criticism it might sound a bit harsh, but when I was done watching your cinematic, I felt you really rushed through this, and just pressed the submit button.
Yes Cinematics don't require real testing, however that doesn't mean it should be a category to be underestimated, obviously we can't expect a movie that will blow us of the screen, when you don't have too much experience with cinematics yet, but try to make more of an effort next time.
Terrain and Environment:
Well this speaks for itself, very poor, you barely used doodads to make outland terrain, you used some cliffs, try to get rid of the cliffs in a cinematic ans use the height tool instead.
Camera Motion and Control:
Specially with Action sequences, try to make a bit more of an effort in using more exciting camera angles, a shot from the feet facing upwards, close ups, overhead etc etc.
The amount of motion may be upped by allot, camera´s that are not moving, are going to bore the viewer quite fast.
Story and Characther Build:
Try to take into account that when you are trying to use your own story in mix with already written stories, you keep the terrain a bit in order, cause the well isn't Outland and neither are the orcs of Grom (untill a certain point).
Other then that, your story is very blunt, cause you are trying to explain a possible exciting idea in such a short amount of time.
One of them is rebbeling against using the blood of the well, kills his companion and tries to kill Archimonde (Who is lucky to get summoned by Kel'thuzad? I doubt Archimonde needs kel'thuzad's power to Teleport).
Additionally I think you kinda killed your story by letting it end the way it did.
Ask yourself this after watching your cinematic, am I really excited to know what happens next? thats how you should let your story evolve.
Animation and Interaction:
Your action animations are decent, Animations and Interaction is Vital part of a cinematic, they give a certain realism to your cinematic, if you misplace animations, it can really kill your entire cinematic, and yes, thats really true, this is exactly the reason I always take this in account when I review a cinematic, and in your cinematic I have a perfect example of what I mean with the above.
When shamu just attacked the gaurd, he runs through him while the gaurd is playing his death animation, that is something that you really would want to avoid, your entire cinematic doesn't have to be realistic (we're making fictional movies for the biggest parts) however certain things need to be correct.
Apart from that, When two people are talking to another, one doesn't go around sitting on the ground.
Simply add a trigger called "Animation - Play Unit Animation (Specific Rarity)" when two units are interaction with another, this will make sure they do the standing breathing animation, but not other additional animations.
Music and Audio:
Basic music, nothing really wrong with it in particular, and nothing really to add here, other than, try playing around with custom music, and specific sounds to illustrate attacks or certain events in the Future.
A 2/5, but don't let that get the better of you, see it as a aim to make better cinematics than you have just made.
I would cast to not approve this map, until further improvements are made.