Wow this thread has gone on for 7 pages :S...
As for whether the Prat is Balanced or not... I reckon it's balanced if you consider the big Picture..
The Roman leaders potentially and Arguably have the weakness trait in the game... (Imperialistic) Ironically though, the trait helps you settle that Iron Site quickly.
There are Aggressive, and to a lesser extent Protective, Charismatic and possibilty Creative leaders that can counter or at slow down the Pratorians.
Aggressive & Charismatic for obviously the Shock promotion.
Protective for CG2 Archers which are dirt cheap and cheap Walls. (I never build any walls in my game with the exception of the Celts and Spainish). This is assuming you do research Archery.. most people don't becuase it's a dead end tech. Also if you strategtically settle in place on hills.
Creative for the cultural defense, hopfully you can reach 500 Culture points before Roman DOW you but this more of a indirect effect.
Not to mention all the leaders that have UUs that come before Patorians which you could potentially rush the Romans before they reach Iron working and Iron.
Looking at the big picture the romans are more or less quite balanced... you could more or less say half of the leaders have some kind of method to counter the Pratorians (can't be bothered counting) and if you happen to be in the unlucky half, learn to play Dipolmacy.
Sure comparing Pratorians to swordsmen, other UUs, Pratorian natural counter and it's cost. It Appears the Prats are overpowered but when you combine it with leaders that have relatively weak traits and everythng else in the game it more or less balances out... unless of course you're palying unrestricted leaders.