Of course, its short !
Like the battle between Yuriko & Azumi... too short too
Its because they designed the campaign to be short so they can move forward & start other projects while they can sell the expansion for many bucks
Looks what happened with C&C expansion.... its become worse & worst each sequel too...just add some few map & some few units, voila... they can sell that exp for US $ 20 & that's why everyone want to play in gaming world... easy money !
Crusader is right Its an expansion. It would probably be much longer if it was a game but then the price of it would be £30 or $40.
Also if you use the cheats it even shortens it. So do what I do. Jump in the game complete it. Then Slap a tranier on and have freeky fun.