It is probably the worst out of all the new WHM abilities. Asylum is not that good since the HoT is considerably weak and seems to proc slowly (compared to Regen/Medica II). However, it is useful since it costs zero MP and has a decent recast timer.

Just know when to use it to its fullest potential in addition to Regen and Medica II, like when a tank and the melee DPS are dealing with a large group of enemies; or in Ravana EX when the tank is taking damage while you're kiting the tethered orbs; or even in A4 when you're targeted with that brutal DoT.

It would be much better, though, if it could be affected by Divine Seal.