The computer level used in the Demo is actually quite low compared with the computer the normal game will have/has. The computer knows how to block and dodge, but the demo shows you maybe a level 4 computer, with a level 30 of HP and brave. That's actually low compared with what the computer can toss at you when leveled up to its maximum.

Related to the attacks, the computer can be quite doggy with you, it will break your soul if you're not ready for the battles, and will not doubt using summons when it needs them. Be assured, the game has quite good computer levels.