The problem with Ultralisk in the TvZ match up has been heavily discussed in the previous weeks, and I believe there are more things we can look at instead of just nerfing Ultralisk.
While others are studying the builds in the recent TvT games, I am actually more interested in the choices and transitions in general. The early game dynamic of the Terran mirror match has changed in Legacy of the Void.
This is arguably one of the best TvT builds out there now. It has a deadly timing attack with Auto Turrets, Tanks, Marines and Medivacs. But at the same time, it has a strong economy back up for a macro game.