I managed to hold two units of Gaesatae with two units of early triari this evening. I suspect other good phalanxes could do the same. It was fairly easy as the gaesatae were easily detached from the main Gaulish army and so could be engaged head to head by the triari. It was then like a Mexican standoff - neither seemed to really hurt the other, but it looked like it could go on all night. It gave me the time to throw some javelins and charge some cavalry in their rear - even so in one scrap, my cavalry (Roman generals with 2HP) got awfully mauled down to 11 men. Perhaps more significantly the triari bought me time to rout the rest of the army so that eventually the gaesatae's morale crumbled.

I've been struggling to find a use for my triari - too slow to suit my still of play and certainly too slow to be be a counter to cavalry - but now I may have found one.