Do you mean King Krush? I don’t recall whether the abilities in question are bugged, to be honest… This needs some testing, ideally — with a testing partner. If this behaviour can be confirmed to occur consistently, then it might stem from another root cause, most likely related to poor programming… I’ll try to explain what I mean.
What I assume is that some abilities might be coded like this: do something, if it deathblows, cast this ability again. Another, seemingly unrelated, example: if Ragnaros’s ‘DIE, INSECTS!’ gets corrupted by a cursed treasure, he takes damage every time the ablility fires. Consequently, I would assume that some abilities are coded like this, which results in the bug with freezing — the next iteration, which is treated as casting a new ability, being lost to the freezing effect, while for Y’Shaarj’s Defiled Attack it’s different. Such sloppy coding…
If this little… theory is true, then they should actually address the root cause and organise the way such abilities are cast properly.