As it stands the two-handed weapon focus group is by far the worse for a few reasons:
2h is mechanically inferior in almost every build, the loss of AC is rarely compensated by the small increase in damage and +1AB
It lacks diversity. You are stuck with x3 or 19-20 x2 weapons by default.
You require an additional feat (Exotic) to use a 18-20 weapon. This feat also enables you to use some 1h weapons (Katana and Bastard Sword). Should be noted that 1h edged has 18-20 weapons included and Polearm has both 1h and 2h options included by default, no need for an extra feat.
No piercing damage option.
My suggestion here is just to add more options to the two-handed focus group. Add every single weapon that is Large or Huge to the two-handed weapon group. This will barely fix the issues I mentioned above (the only direct point it solves is the last one, with access to piercing damage). If it is bound to be the worst focus at least make it more varied in terms of raw weapons.
I should note that there is precedent for this, for some reason double-weapons are both two-handed and polearm, if a dire-mace can be considered a polearm and two-handed I do not see why a scythe or colossal spear are not considered two-handed.