icy talons bug?

so heres the thing i was tanking with my dk for a long time and i created a warrior tank.it says that thunder clap reduces attack speed of enemy by 20% (improved with talent) and i can see clearly theyr attack speed is reduced nicely, but when i use icy talons on my dk it should reduce attack speed of enemy by 50% or more with icy talons but when i use on them it seems its not working. so idk is it bug or im mistaking in something.Maybe it doesnt stack with frost fever idk why but it seems like theyr attack speed isnt slowed.I can see clearly attack reduce when i use thunder clap but just cant when using frost fever with icy talons

these do not stack
Icy Fever - Thunder Clap - Judgements of the Just - Infected Wounds

You can have all of them on target, but it will only slow attack by 20% or whatever it was

no u miss understand me i was thinkin 1 spell. its like icy fever doesnt slow attack speed of trash mobs and bosses but thunder clap does i could see that very clearly that thunder clap slows attack speed of trash mobs but its like icy fever doesnt do sh1t except deal periodical dmg

Hmm, couldn't find anything in bugtracker, maybe its worth investigating and create a report if there is something.

i just saying i was dk tank 2 yrs now bug when i used thunderclap there was so huge diff in attack speed of mobs