Barkskin isn't working towards Cloudkill.. bug or feature?
As it is now, there's really no means of countering a stuck Cloudkill except for having insanely high def.
It can't be Mirrored Destiny'd and apparantly not Barkskinned either, so, whoever lands the Cloudkill through evade first wins.
Barkskin only affects inflictions, cloudkill is NOT an infliction so there is no bug.
Cloudkill should be affected by mirrored destiny (if is not an infliction then it have to be a delayed direct attack) but it doesn't (that's the bug).
To counter the cloudkill -> giants strength + astral body combo you can use magic shield; there is a bug where astral body fails because you can't stack buffs (even if it's not a buff). Using infirm may help too. Anyway, cloudkill is going to be nerfed in the next balance update (4 days ago a moderator said that it's coming in about 2 weeks)
@coto013 good that a balance is coming for it, in this case GS and AB wasn't even used...