European servers

[Alukah]

This is because the effects of an ability are tied to the animation, so the DoT will only become active (And therefore subject to Bane/Fester) once its animation completes. This is a design choice by the devs and not an issue to do with lag or latency at all.
Such a lack of understanding shows you might not know what you're talking about in other areas.

"I am right and you're wrong" is all you're saying.

Bane/Fester right as the debuff icon is applied and the game may still fail to register it.

Also buy a dictionary and find the definition of instant.

[saeedaisspecial]

"I am right and you're wrong" is all you're saying.

Bane/Fester right as the debuff icon is applied and the game may still fail to register it.

Also buy a dictionary and find the definition of instant.

As soon as the icon is visible on the mob, you can Bane/Fester for the effects. Yes, it says instant but you still have to wait for the animation to complete. Like all abilities in game.
Also, go ahead and read the descriptions of abilities such as Bio, and Miasma II. The cast time is stated to be instant, the effects are not (as they are subject to the time it takes for the animation to complete).
Please, go and do a little research before lashing out.

[Alukah]

As soon as the icon is visible on the mob, you can Bane/Fester for the effects. Yes, it says instant but you still have to wait for the animation to complete. Like all abilities in game.
Also, go ahead and read the descriptions of abilities such as Bio, and Miasma II. The cast time is stated to be instant, the effects are not (as they are subject to the time it takes for the animation to complete).
Please, go and do a little research before lashing out.

"and the game may still fail to register it." Reading 101, you failed it.

My last reply to you, you're free to believe whatever you want to believe.

Have a nice day.