Regarding Elite Mark HP

[Feronar]

I think they should have it scale up automatically if a large numbers of players attack it, similar to World Bosses in WoW.

The way it works in WoW, a world boss might have say... 5 million HP for 10 players. If an 11th player attacks, the HP will scale up to 5.5 million. If 40 players attack, it will scale up to 20 million. The scaling up happens at the moment each additional player hits the boss. The HP percentage (current HP / max HP) are not changed when the boss scales up for more players.