actually it is mathematically inferior in almost every respect.
The damage reduction is not strong enough to counterbalance the weak base stats and SV's regen and healing boost are actually stronger than 15% damage reduction in the first place unless you are taking massive amounts of sustained damage (as in enough that you should be dead before the adaptive helm actually has any benefit compared to SV)
The damage reduction needs to be closer to 30% before it'll be a competitive item from a straight numbers standpoint, otherwise it'll always be a "get this after SV if you have extra gold and an item slot you don't need" item. Until it has identical stats to SV and solely different based on the passive, there's not even a chance it'll compete.