Dark Seal Merits - Explanation Please?

I'm reading Dark Seal merits. I put on in to play with, but beneheath the description of the ability it says

"Shorten Recast time of all dark magic spells by 10 percent"

Is that conditional? Does Dark Seal need to be in effect for this to happen? Wiki doesn't mention much about this.

If it's only when Dark Seal is active, then it's not worth my interest, but if it's all the time, it might be.

Just with Dark Seal active.

Assumed so. But it wasn't specific. Bah.

1/5 Dark Seal gives you everything it's worth.

4/5 Diabolic Eye is still even better with Relic +2 hands as well for a bit more time on that wicked +35 accuracy. Relic +2 Head's duration increase with Dark Seal only affects Absorbs and Dread Spikes, and th'hell would you use Dark Seal on Dread Spikes mind you, while it doesn't work on Drain II which is what you'd really want the duration buff on. Also ironic that Dark Seal didn't work on Drain II anyway, seeing the latest patch notes.

It did work before the patch, they don't even know what they are talking about in their own "fixes".