Q. What's your opinion about using adjectives like " very" for special emphasis? XYZ is very vital to the...Of course the " vital" is sufficient and correct; it doesn't need " very."
A. You're quite right. Something is either vital or it isn't. " Very" would be superfluous in the sentence you gave. We can see how ridiculous it is if we put another adjective in its place:
XYZ is slightly vital to our project.