I would not buy any GPU with only a 3 month warranty. No display connector of any kind also ruins the resale value. Any "mining specific" GPUs that I have seen so far have been roughly the same price as "gaming specific" models and equal in performance, so there's no reason at all to buy them imo.
One reason I can think of is actually using the 19 slots in the Asus motherboard. For what I've heard you can only do that with these cards (that have no video). Other than that, maybe I need to rethink it 
Yes I think it should work like what P106-100 performs in Asus B250. As I remember, there's a topic which many guys showed they successfully installed 19 or even 21 P106-100 in B250 mining mainboard. Actually, P106-100 is good deal for me, its price is reasonable and achieve high hashrate. As I heard that Inno3d P104 card could hash 35Mh/s and price is around 425$ (not confirmed it yet, I'm waiting the answer in next 3 weeks). If it's the case, it is a good deal as well.