Guild Wars 2

Signet of might and nothing can save you both cause attacks to be unblockable. Signet of might has no cast time meaning you can activate it while casting another skill, extremely useful if you notice your execute is about to be blocked. On the other hand "Nothing can save you has a cast time on it so if you notice your grave digger for example is about to be blocked you have to cancel it, activate the shout, wait for the shortened cooldown then activate it again.

When people give Anet kitten for the retrded way they handle class design, necro especially, you see why.

NCSY can corrupt up to 10 boons (2x target) into vulnerability (10 vuln on every enemy), last for 9 seconds and have the cooldown reduced to 17 seconds.
That is why they put a casting on it: it’s really strong.
You can also active it Before using Gravedigger.

But yes grant it no casting time will be really useful.

Anyway, there’s already different treads about that possible change, read the forum for other discussions about that skill.