PVPers are exploiting the "Teleport to Dungeon" function, here's my suggestion.
Teleport to Dungeon is normally used when you're grouped up for a dungeon, it allows you to instantly teleport in and out of the dungeon when you're out of combat. Unfortunately, more and more players are exploiting this function with macros in PVP giving the other faction no counter-play to little or no consequence. Here are some examples that I've observed being used:
In general:
-When a player is sapped, since they're still out of combat they can teleport to the dungeon to not only escape but to also remove sap and then teleport back out.
-When a dead player resurrects they instantly teleport to dungeon to escape.
Class specific:
Rogues-
When the rogue is stunned and/or about to be killed they use a macro that trinkets out of stun, vanishes and teleports to dungeon all within an instant to escape.
Hunters-
When the hunter is stunned and/or about to be killed they use a macro that trinkets out of stun, feign death, and teleports to dungeon all within an instant to escape.
Shamans-
When the player is dead they'll reincarnate and instantly teleport to dungeon to escape.
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When they teleport to dungeon they heal to full and buff up with their respective class buffs as well as food buffs and other buffs, as well as bubbling up right before teleporting back in.
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My suggestion on how to fix this:
If you add a short 2-3 second cast timer this would immediately fix this problem. The instantaneous nature of "Teleport to Dungeon" is what makes it pretty much impossible to do anything against.