Post Kmst PVP videos here.

Based on those videos, yes, if the player was in range when the avenger was thrown, it will hit even if the player is on the other side of the map.

Is that intended, or just it's lag? Hard to telll

I'm assuming it's the same with monsters. As soon as you attack, it checks to see if the monster was in range of the attack. If so, it counts as a hit. The player was in range when the attack was triggered, but not for the animation. Ultimates are a good example of this. As long as the player was in the 400% range of the Ultimate when it was casted, they will get hit by it regardless of where they were during the other 2-3 seconds of the skill.