It's easy to blame Activision for the bad reception TWO, not one, Bungie games have received. It's not like their union was forced upon Bungie.
I don't know the numbers currently for D2. But, D1 was very big, on the new IP scale. So, it is safe to say that the Destiny franchise is very significant. Certainly not make-or-break for Activision. But, it is definitely worth some real money, considering that it has a fairly sizeable, extremely dedicated fanbase.