Basically, if a debuff is applied on the target, it will remove a similar debuff (with the same effect), no matter if the currect debuff is "stronger" or "weaker".
For example:
A target has Cone of Cold debuff (reduces 60% speed), if you Frostbolt him/her (reduces 50% speed), it will remove the CoC debuff and apply the new Frostbolt.
Note: you get those numbers with talents (Frost)
How should work:
The strong effect should continue, instead of being removed by a weaker one.
Proofs:
Bug's screenshot (CombatLog) - http://i.imgur.com/PF7vHxA.jpg
Noone 3 - Frostmage - http://www.youtube.com/watch?v=Ku0xSDBrtVM
Note: check @4:00, the rogue got CoC, then Noone casts Frostbolt, you can clearly see the CoC debuff after the Frostbolt hit the rogue (2nd debuffs on Rogue's frame)
Basically, if a debuff is applied on the target, it will remove a similar debuff (with the same effect), no matter if the currect debuff is "stronger" or "weaker".
For example: A target has Cone of Cold debuff (reduces 60% speed), if you Frostbolt him/her (reduces 50% speed), it will remove the CoC debuff and apply the new Frostbolt. Note: you get those numbers with talents (Frost)
How should work: The strong effect should continue, instead of being removed by a weaker one.
Proofs: Bug's screenshot (CombatLog) - http://i.imgur.com/PF7vHxA.jpg Noone 3 - Frostmage - http://www.youtube.com/watch?v=Ku0xSDBrtVM Note: check @4:00, the rogue got CoC, then Noone casts Frostbolt, you can clearly see the CoC debuff after the Frostbolt hit the rogue (2nd debuffs on Rogue's frame)