So make a party of all halflings and see if it is more powerful than a normal mixed party. This is a playtest.
We did some limited tests and halflings are interesting in combat.
They hit more often but do far less damage than a Warrior. Mainly because a warrior adds his MDoA die to the damage roll. This bumps his damage up just enough that a halfling is not quite statistically as powerful as a simple sword and board type fighter (fighter has higher damage output, wider range of weapons, and higher AC).
While you do get more criticals, you will find that the extra attack actually lowers the to hit probabilities the higher your opponent AC's get. One bonus is that AC's of creatures in DCC RPG are no where nearly as inflated as in 3e/4e.