Some games such as WoW and Rappelz have a threat level in the game while Guild Wars is monster attacking the first one to aggro them or target with lowest health. ANet can simply implement a threat level system in with several skills which I will show below with PvE-Only skills and the PvP version based on threat level. However you cannot see your threat level such as meters and hints to show it.
Threat level is run in percentage, monster attack player with highest threat percent in their rating, threat percent increase depend on the damage they deal while supporting class have a base starting of high percentage than other class.
War is a class that need to tank in order to be party-effective. A war that run off to attack enemies' squishies is just another offense class.
Aggrevating Shout [6 Adrenaline | Strength]: Shout. All nearby enemy have 0..75% threat toward you. You lose all adrenaline.
Casters and Squishy such as monk and ele must NOT in any way have access to threat level management or else that would ruin the point of war.
Assassin with the above rule of threat would basically get screwed since they deal massive damage so they need a threat management skill in PvE.
Critical Stealth [10 Energy | 3/4 Cast | 30 Recharge | Critical Strikes]: Enchantment Spell. For 1..9 seconds you have -0..50% threat level. Refresh everytime you critical.
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For the PvP version, threat level don't exist since we're not integrated with microchip in our brain. There is a way tho to alter the percentage or getting targeted by altering the enemies greatest tools... *drumrolls*...their radar.
For War:
Aggrevating Shout [6 Adrenaline | Strength]: Shout. All nearby enemy can only see you as their enemy in radar. You lose all adrenaline.
// This work by making all the enemy except you disappear from radar, does not remove their ally tho.
For Sins:
Critical Stealth [10 Energy | 3/4 Cast | 30 Recharge | Critical Strikes]: Enchantment Spell. For 1..9 Seconds you cannot be seen on radar by enemies. Refresh everytime you critical.
// This could be very useful in AB used for a quick escape while could be highly valuable comparing with Critical Defense. This skill is also in critical strikes so caster cannot use it very well comparing to assassin.
Z

Besides, going "GRAHH!!!!!11!1!1!one!" to get attention isn't the human language either
. None-the-less. 