I am like the worst at arena but here is my two cents.
In that particular match..
I noticed that you used your fear defensively, when you didn't need to... For example at 1 minute. You weren't in position to get a kill and were both far behind the kill target.
Living has arcane torrent and psychic scream so it is his duty to silence/scream as interrupts on casts, while you both sync burst dps.
A couple of times your positioning was kind of awkward because you were getting kited so hard.
Sometimes, if you're being kited way behind the target, its okay to turn around and nuke the hunter when their healer is los/oor. It just puts pressure on the healer and forces them to stop and heal the hunter. Better yet, when dps are tunneling on you, sometimes you can pull them further away from their healer and get a kill by isolating them.. but watch your dps because you are also away from your dps lol =].
At the end of the video, I would have gone on the defensive/los as both of you were running oom and the warrior was on him. The warrior should be able to burst through his remaining mana pool quickly. You kinda ran behind the pillar and back into the open. I think you could of had it there.
Also, use bandages.
Also, kill the pet. Kill command/pet damage sucks.
Make sure you're not just reacting.. You need to be planning to go for the kill. This for example can be saving your fear when your arcane torrent is about to come off come cd, and have the warrior have a fullish rage bar as you go for the kill. Finally, I understand you're playing offensively, but i think you should of chosen to mitigate more damage, by making use of los more. This effectively puts you ahead in the mana game. ( Get and use a spirit stick too ).
All easier said than done. You did a good job keeping yourself and him up until you ran oom. There may be things you agree or disagree with but hopefully something helps you guys out. These are just some(many) thoughts.
Good luck.