Regen reapply on last second causes No effect

[Pacifyer]

I am playing WHM and I noticed that oftenly if you try to reapply Regen on your tank on the last second timer it results in No effect message and the buff is not applied to target.

I can't say if it is something with specific additional buffs on target or lag but I have met this behaviour multiple times. I hav espent both mana and GCD in vain.

This may however have something with WAR being a tank cause I can't recall these problems be there with PLD being a tank. I remember exactly being able to 100% reproduce this bug on purpose.

[Venruki]

If you clip a healing over time, or damage over time effect(recast it before it ends) and you had a buff to your stats on the first cast, it won't overwrite, and give you "no effect".

[Calyanare]

If you clip a healing over time, or damage over time effect(recast it before it ends) and you had a buff to your stats on the first cast, it won't overwrite, and give you "no effect".

This. The game won't let you overwrite a stronger effect with a weaker one. SCH Protect/Stoneskin can't overwrite WHM Protect/Stoneskin, and if you had some kind of buff (like Divine Seal) the last time you cast Regen that is no longer in effect when you try to cast it again, it won't overwrite then either.

[Geobryn]

yup, you can not overwrite something which is better than the thing you are casting
as dots/hots retains the buffs even after the cooldowns are already expired thus can not be overwriten

and its not only cooldowns, any buff will do that
for example archer +10% crit buff
lets say crit buff have 5 sec left, i pop 2 dots (20sec), crit buff dissappear, i can not use dots again as there is gonna be no effect until i buff myself up or the dots expire or i pop something stronger like some "cooldown buffs"