The common argument is that when cards are costing hundreds or even thousands of dollars, the fault is with Wizards and the reserve list, or the over inflation of card prices on the secondary market
This text applies perfectly to what Fractured Sanity does since it makes your opponent mill a ton of cards
At the beginning of each end step, if you gained 3 or more life this turn, create a 3/3 white Bird creature token with flying and "Whenever this token attacks, target attacking creature gains flying until end of turn." Whenever Gwaihir attacks, target attacking creature gains flying until end of turn
Basic energy cards are the most common
They probably put this ability on a creature to make sure that it was more easily answered
Outside of that, I don't see any other payoffs for the lifegain