Average Effective HP (AEHP)

The Average Effective HP metric describes the expected survivability over an infinite amount of hits: Meaning the tank deflects some hits, the enemy crits some hits and so on. The assumption that the enemy has no debuffs nor buffs in effect is applied.

The Average Effective HP is calculated by:

$AEHP =(Total Hit Points +Temporary HP + Barrier HP + Dig In Shield )\\~~~~~~~~~~~~~~~~*~(1+Defense)\\~~~~~~~~~~~~~~~~/~(1+CAUptime *(Combat Advantage_{Enemy} - Awareness))\\~~~~~~~~~~~~~~~~/~(1 Crit Chance_{Enemy} * (Critical Severity_{Enemy}-Critical Avoidance)\\~~~~~~~~~~~~~~~~/~(1-Deflect+Deflect / (1+Deflect Severity))\\~~~~~~~~~~~~~~~~*~1/(\prod Mitigation Multiplier)$

The formula is quite hard to understand and to properly explain. For now, I'll leave the explanation out.

Example: The Tank has 1 000 000 HP including all bonuses from VIP, food, gear, etc. The Tank does not use Dig In nor mitigation skills. The Defense, Awareness and Crit Avoidance stats are capped (90%), Combat Advantage is up all the time, Deflect and Deflect Severity are both 50%. Then the AEHP is:

$AEHP =(1~000~000+0+0+0 )\\~~~~~~~~~~~~~~~~*~(1+0.9)\\~~~~~~~~~~~~~~~~/~(1+1*(0.9-0.9))\\~~~~~~~~~~~~~~~~/~(1+0.5 * (0.9-0.9))\\~~~~~~~~~~~~~~~~/(1-0.5+0.5/ (1+0.5))\\~~~~~~~~~~~~~~~~*~1/(0.8)\\~~~~~~~~~~~~~~~~ = 2~280~000$

You can use Janne's EHP Calculator to test with different values.