That video doesn't show a lot - just one incident, certainly not "the biggest kser in Shaiya" nor "the whole of Mait".
Why did you back off after almost killing that orc? It was as if you were inviting him to attack.
The video also showed an extremely busy area - you were also in competition with another party for the first orc in your video, which they hit first (and got the kill).
I would suggest trying somewhere else. Look here
for places to go at your level. Outside Mait is one of the busiest areas in the game, and at 52 & 51 neither of you would get any XP there anyway.
If you want to report someone for kill stealing, you need to show more than just one incident.
You need to show that you have asked them to stop, but they have carried on anyway. If you can show that then LordKotaro has given the means to report someone.