The following only applies to PC:
Torb needs a complete rework. He is just completely unviable against a team with any slight form of communication. Most torbs end up staying way far back and building constantly only for the turret to be destroyed with ease seconds after. This means we don't see a lot of armor most of the time either. It has gotten to the point where in Comp matches the team with the torb loses 90% of the time.
I'd propose first off increasing the time to lock on auto aim by .2 seconds or so. Just enough time to peek on it easier and destroy it solo easier. However, Torb needs options. Maybe give him the option to, also engie, build an additional level one turret instantly. Have him sacrifice 25% meter to do this. The turret could be perm level one, but would encourage more mid to front line Torbs. It would completely change defensive options and make him viable while still being easy to deal with.
hero stacks are another issue, and I'd recommend rolling damage drop offs for 3 or more of one hero.