How troll is new Rylai's on Shen?

So Rylai's seems semi stupid to build on a tank and 3k gold is a lot to invest on Shen for an item with no armor or MR, but I got to thinking about what it gives him and was wondering if mid or early game (if you're getting fed vs an AP lane maybe?) it would ever be worth building?

Here is what it does for you:

400 HP and 100 AP plus the passive, which is 100 more AP than any item you likely build on Shen and equal HP to Locket and SV, 50 less HP than sunfire and BV, 100 less than Omen, and 400 less than warmogs.

It adds 40 damage to his passive proc, which is pretty standard for Shen items.

But here's where it may provide something good:

It adds 60 damage to q and a 40% slow for 1.5 sec

It adds 60 damage shielded to w (which if leveled last like it generally is means it doubles the strength of w for most of the game)

It adds 50 damage to e, and it's probably not useful, but they are slowed for the duration of the taunt

And last but not least, it adds 135 hp worth of shield to his R, which is a little over 50% of base at rank 1, and almost 20% of base at rank 3.

The slow on q seems like it might be beneficial in some situations, and the bonus damage on q seems good for harass in lane. Most importantly it adds over 50% to the shield on your R until level 12 (when it drops to like 30% or something that is still pretty useful), which seems like it wold be really strong in helping out bot lane getting ganked or stuff like that during early/mid game. Is this ever worth building, or is my thought that it might be useful not entirely insane?