The only time it seems to really help vs a non baffled is at low boost situations. Under full boost, without the baffle, you can bet you're filling up the while IC. Low boost, however, the air doesn't need to expand just to fit into the core, so it goes straight into the fins from the input end tank, generally only utilizing half the core. It may only use half the core, but it doesn't need to use more than that in that situation.
Probably one of those minimal gains for the added expense situations. Just like TGV's. Is pulling the manifold, porting the tgv's, sealing the holes, and putting it all back together worth the 5hp? Probably not, unless you already have a reason to have it all apart.
That being said, I would baffle my end tank if I was building a core from scratch like that. It's only about a $20 difference since you only need it on the input side of the core, and it definitely doesn't hurt performance. I wish I could have put one on mine, but oh well. It's a small enough core that it won't make a big difference.