Originally Posted by
Zubacz
When you push higher keys, you need a bit of luck. Some keys are just dead keys. For example, we found some instances are not doable on Fortified (Nerthalion's Lair above 12 or so, because of the scorpions, Vault, unless you skip the first miniboss), more are not doable on Tyrannical (DHT last boss, Halls Hyrjya, Eye of Azshara last boss). Court of Stars is not doable at all above 12. As you get more gear you can push higher, but it will always be those instances which will cause trouble, because the given boses or mobs scale to do ridiculous damage.
My advice, avoid those keys. If you are doing 10s or higher, you probably have a dedicated group, so just do another key and hope to be more lucky.