Of course that sort of thing is far less common in the south anyway.
I guess Orissa is a northern state too. I would say 80-90% of attacks on Christians happen in that state and the tribal areas adjoining the state.
As for Muslims, yes most attacks happen in the north. West India doesn't like to get left behind though, as we know all too well. Bengal is pretty peaceful, considering how large the Muslim population is there. Assam on the other hand.....
Yeah, religious strife has for the most part not been an issue in Bengali history, especially when compared with other parts of India. The partition of Bengal was the greatest crime of decolonization. In Assam the Hindus are Assamese and the Muslims Bengali, so that there's an ethnic dimension to what looks like religious unrest.