Well, I went with the assumption you are sticking with the free synch monitor
And I am under the impression that during raiding both cards (1060 and 480) will perform pretty much equal to each other.
As for crossfire, I think WoW still does not support it making it useless. Also, crossfire 480 is actually worse than a single 1070. Not to mention possible stuttering, games not supporting crossfire etc. So I would not go for a crossfire set up.
I haven't gamed on anything above 60 Hz, so I cannot comment on that. But the 1070 blows the 480 completely out of the water. You can still get the free synch screen if you get the 1070, it will just not support free synch. But should still allow to run games at 144 Hz (or w/e Hz the screen has).
A note to make about the 1070 and DX12. The 1070 could possibly not have proper DX12 support, we do not know yet. So take this in account. It might be 'useless' in 2 years. Or when Nvidia decides to drop support for the card, the moment the next series gets out with better DX12 support.