a few questions...

[bovi]

Are you kidding?!? One time had my 82 1exp/1 weapons and armour Pricipes attack 54 two gold chevron and 1 weapons/armour Cidainh (Celtic Chariots) of an enemy FM and the Pricipes killed all of them in exactly 10 seconds! The chariots didn't even get bogged down, and the didn't cause a single casualty among the Principes!

That would be because the AI used them incorrectly, charging missile troops headlong into a thick mass of people, with javelins no less. Like elephants, the AI has no idea how to use special units.

The vanilla chariots would die extremely quickly from any missile fire. One volley of slingshots or two of arrows and they would all be either dead or rampaging, including the egyptian general. The higher mass in vanilla made them somewhat more effective at smashing into things though, but they would still die quicker in melee. Perhaps you should try a missile chariot charge against principes in vanilla and compare.