Why... so... Lame?
So DeffRollas are now the DEATH OF MECH! Yeah, whatever.
Like Nob Bikers and IG Air Cav alpha-strikes, it'll take about 3-5 months for the Deff-Rolla spam lists to come and go. Afterwards Mech will still be king, because we'll all still be playing 5th Edition 40K.
But of course we've been here before. Why face reality when you can wish it away?