that's just renters following market demand, it isn't really abuse any more than someone paying a lot is abuse to the people that wanted to pay less. Owners cant set parameters for how long you're allowed to rent something at dirt cheap mid-season pricing, so they might have only wanted to let you use it for that one day, and they could cancel for any number of reasons (including wanting the CP themselves)

I recommend renting just after the 24hr marks on season timer, so that rentals arent dropping an hour before season end, you will have more notice and be in the best position to react to any cancellations. Until improvements are made to make this easier, people have to compete for the best rental strategies as much as they compete for the best battle strategies. Knowing the CP values of various cards may help a lot in that regard.