I made my own calculations and reached the same conclusion: I would be losing DEC (on average) if I rented just to climb to the next tier.
Also, when I stayed in my own tier, I was able to lend some extra cards I had in order to rake in even more rewards :D
Yessir :). Rates were as bad as 35cp/dec at EoS. And reward pool today? Dayum.
Indeed; the whole rental system is horrible on the "End-Season Day", making the whole thing unprofitable.
Owning the assets and renting is, obviously, the best option.