Feels like it'd be silly strong on him. Aids his tankiness and his damage all around, his Q alone lets you get the proc all the time and the guaranteed 35% slow in an area (along with the AA damage being boosted and dealt in an area) is not bad at all.
I only tried it in a bot game, so I can't say I've really tried it out, but it seems good on paper.
The problem I'm seeing with it is that Ryze generally wants to machine-gun combo with very little time for AA's in between spell casts. That being said, it's really hard to properly gauge IG's effectiveness in general just because the impact of having basically a new spell is extremely difficult to analyze. --- "We all wear masks, and the time comes when we cannot remove them without removing some of our own skin." - Andre Berthiaume, Contretemps