Sorry, I don’t think I can directly state your character’s name and guild as per forum rules and you seemed to be offline when I tried to send in game whispers. I missed your chat messages as I was kind of out of it. My apologies.
As per tips
#1 Set up your gateway and lock portal soon after coming out of the gate. Behind cover is preferable but the majority of the importance is to place them close to each other, then move away from them but still in range to teleport when things get hairy. Bonus points if the gateway takes you even further away than the direction you teleport in from.
#2 While Agony and Corruption are important, Unstable Affliction is our most important DoT and you should start getting them out as soon as it’s safe to free cast. This is because healers who dispel it get silenced, making it both a payoff in and of itself, and making healers sweat each time they feel forced to dispel.
#3 I was able to just out of nowhere get the other team’s health chunking down by making sure I had dots on all of them, then using Dark Soul: Misery, Soul Rot (gains benefit from the dark soul haste and isn’t the end of the world if kicked due to it only locking out our nature school and not shadow), Rapid Contagion (PvP talent) to get the dots ticking down even faster, dark glare to extend the Dots, and following up with Drain Life (using the Inevitable Demise talent) for a final big burst and large self healing as safety measure. Then you can try to kite and let your spells do the rest.
Hope this helps and best of luck in your PvP endeavors!