Guild Wars 2

Just a couple of minutes ago i was testing this Earth Trait Diamond Skin: remove conditions while your health is above 75%.
So i laughed at condi Necro while i was defending a base with 100% health. After about 3 seconds i was still on 100% (maybe 95%)health but suddenly that necro was able to put number of conditions on me at once, and i didn’t even try to dodge, because i was expected all these condi will be gone in next second thx to Diamond Skin, but nope his conditions stayed on me and i needed to use my other Skills to removed them. And he did it every time we met!
So can someone enlighten me what have i’ve been missing here? Why condi on me haven’t been removed? Or this trait only remove one condi per second? Or it only works in earth attunement like Stone Heart, which is by far superior trait in this t3 line.
I would understand if condi wouldn’t being removed when my health drops below 75%, but i was on 100%!
Sorry for English …

It’s only when you got hit. And it has 1s cool down. If the necro only put the condition on you and walk away, the condition won’t get cleansed. Diamond Skin is not good without going pure tank. Water traits is mandatory.