Storm, D/T, and Roto all "share a base resin"! I know, I bowl with or have my stuff drilled by guys that work there. All three tweek the formula and add their own cores to make up three unique and different product lines with distinctively different "feels" to them.
On the subject of cracking, the base resin was the problem I was told by a VERY reputable source. The replacement resin is of the quality initially requested. Problems are apparently gone because I have a D/T and a Storm from this batch and they are AWESOME!
I am pretty certain that no Ball manufacturer makes their own base resin and that it is all made overseas and shipped here to be "finished"... I am certain somebody will chime in and enlighten me... I recall a discussion on this subject way back in the day... something about stringent EPA rules...