The Tropical Storm, Power Groove, Tornado, Flipside Wild and Pre-EBI Scouts all had very mild asymmetric cores in them.
IMHO there currently aren't any entry level asymmetrical bowling balls for one very good reason...
No drilled ball is symmetrical...
If you want an asymmetrical piece with a weaker cover, feel free to take something like a Brunswick Avalanche and double thumb it. The resulting core numbers are transformed from mild (2.548 RG, 0.24 diff) to a more respectable lower RG piece with almost double the differential and an intermediate differential in the teens.
I attended a seminar where that was one of the examples used to illustrate the fact that all drilled balls are asymmetrical. Another example used was a Brunswick Mineralite manufactured in 1948. A standard "label" layout put the Low RG axis at 2.710, the diff. was 0.010 and the intermediate differential (MB) was 0.015.