Spells: refreshing buffs on the mark when old wears off

[DoucLangur]

Concerns necro lvl 20 lich spell "Allure of Death":

The old one is about to wear off, I just casted a refresh and had this symptomatic:

PHP Code:

You begin casting Allure of Death.
You feel your health begin to drain away.
You feel better. 


(this last one came like instantly, and is the worn off message)

After that, the effect was not on me.

My suspicion is that the sequence of events got mixed up here: First, the new spell got applied, and then the old one wore off, clearing the effect. Since this doesn't happen regularly, my suspicion is it only happens if the re-cast of a buff (or only this spell?) lands within the same tic (or a few seconds) of when the spell should wear off.