Anyone know what pressure points (passive assassin line) applies to?

Spell Crit only?

Assassin line Crit only?

Weapon Crit only?

Or all of the above?

It's all. It's better though (or at least, I think personally), when your bar is full of assassination abilities since your crit goes up with every assassin ability slotted.

There is a good description http://elderscrollsonline.wiki.fextralife.com/Assassination+Skills. It's 2% at rank II.

Cas

Does it only work for Assassination abilities (e.g., When you use an Assassination ability.....you gain crit chance) ?

I believe you get the bonus to any skill, since it says: per skill slotted, not used. Hope that helps.

Cas