Rageforged support doesn't work

Rageforged support doesn't work as described in it's description - it functions well with normal self-cast skills, but it doesn't when it comes to triggered skills (even though the description mentions it should). I've tried using it with Cast on Crit (so there's a mana cost) and Invoker's Elemental Expression (no mana cost) - both don't work. From what I've seen it's not a popular problem, but there are other posts that mention this issue.