Unfortunately, you are correct about Rocket Red being built off of the Atom Smasher buck. This means that Rocket Red stands about 1.5 times taller than an average human DCUC figure. Just look at the picture below (NOTE: Mary Marvel is on a flight stand, so don't use her for basis of height comparison).
Seeing as how DC Club Infinite Earths is coming to a close as well as pretty much the rest of the DC Universe 4 Horsemen figures, this is the only Rocket Red figure we are likely to get from Mattel. If you are really a big JLI fan, I would say get him. Plus, given that Mattel most likely still has a bunch of these sitting around in the warehouse, it's entirely possible that you will be able to pick up Rocket Red for really cheap during their Black Friday/Cyber Monday sale.
Hope that helps!