This list is heavily tailored, and from what you've told me, you should beat them in one or two turns
*You need a priest, who is crap and at least 40+ to use arco-flagellants
*He must be attached to a squad. If he's attached to a bolter squad, they will not be able to shoot 24" inches
*Reapers will massacre sisters too easily for it to be a fun game
*Reapers should be able to do damage to arco-flagellants, but they're a lot harder to kill than marines, and half your shots will only wound, and only half of those will kill the models
but if the scorps get in to combat with the Arco - Flaggelants i'm sure that the scorps would lose..but i'm not sure.
You'll have a hard time beating them. You might kill one, he might kill 3 or 4 and your exarch should kill 1 or 2
i can reduce the number of scorps and take away infiltrate and make them stay back incase the enemy gets to close to the reapers. so with less scorps i may be able to have at least 4 reapers giving 16 shots using both units!!
Not sure of this, but I think stealth has been replaced by the BGB, which means they can't infiltrateEDIT: The FAQ doesn't mention the change, like tank hunter and skilled rider. Your scorpions should still be able to infiltrate
You should do well. Good to hear summary. Just remember, arco-flagellants can be fast when they want to