Marauder Righteous fire / Molten shell

Hello, first of all i am terribly sorry if my English is not top notch.

I was thinking on starting a Righteous fire build and here how i plan to build it.

Here are the 3 faces of my passive tree that i am planning on:

Phase 1 - http://www.pathofexile.com/passive-skill-tree/AAAAAgEBBjkZLho-JIsn7TrYPQ89_E99UWBXDVhjXz9qHmo7dqx8u4BWgpuMdozPnjytjcT2xtjPftIh2WHsOPIv9kg=

Phase 2 - http://www.pathofexile.com/passive-skill-tree/AAAAAgEBAdwB5wSzBS0GOQthDc0UIBRNFSAWbxiRGS4aOBo-GmwcziLiJIskqicvJ-0pTypNK1As6TWSNug26TrYOuE8LT0PPfw_J0ZpR35H4kp9SshN4099UEdRYFb6Vw1YY1ivXz9gS2EhZU1noGoeajtuqnTtdqx4DXloeu98u4BWggeCm4TZhO-HdorwjHaMz5AKkFWePKIAo4qkOaZXqW6tjbXytz68n702vorBBMQVxILE9sauxtjKkM9-0IHSIdi92WHZfN0N4XPi6uNq45_kIuhm6UbsOO0g7g7vDvAf8i_yQfJF9kj8S_zF_gr-VP6P

Phase 3 - http://www.pathofexile.com/passive-skill-tree/AAAAAgEBAdwB5wSzBS0GOQ3NFCAUTRUgFm8YkRkuGjgaPhpsHM4i4iP2JIskqicvJ-0pTypNK1As6TWSNug26TrYOuE8LT0PPfw_J0ZpR35H4kp9SshNkk3jT31QR1FgVvpXDVhjWK9fP2BLYSFlTWegah5qO26qdO12rHgNeu98u4BWggeCm4TZhO-HdorwjHaMz419kAqQVZ48ogCjiqQ5plepbq2NtfK3PryfvTa-isQVxILE9sauxtjKkM9-0IHSIdi92WHZfN0N4XPi6uNq45_kIuhm6UbsOO0g7g7vDvAf8i_yQfJF9kj8S_zF_gr-VP6P

I will build my maximum fire resistance to reduce the damage from Righteous fire and then build my maximum HP.

Next is my list of skills gems :

Righteous fire

Purity of elements

Purity of fire

Cast when damage -> Molten shell

Right there is my question will the degeneration per sec of "Righteous fire" could trigger "Cast when damage" so it would cast "Molten shell" to mitigate some damage and do more damage or it wont trigger. But i wish it will because i know that "Cast when damage" has a 250 ms CD, but i hope it would be enough so by the time "Molten shell" absorb the damage of Righteous fire, the 250 ms CD would had reset on "Cast when damage" and recast "Molten shell" again.

Thank you for your reply.