The game and DLCs are totally worth it. I also disagree with statement, "weak the game feels when you're not in a vehicle". I have the most fun when I'm running around with a rocket launcher and mines. Tack on the assault rifle and you have a one man army.
If you have a rocket launcher and mines, you can pretty much take out anyone or bring them down with you at least. 
edit: Disclaimer: I play pretty cheaply. Suicide runs and such, so don't take my word for anything Warhawk. :P
Person 1: Does Valkyria Chronicles have trophies?
Person 2: No.
Person 1: Forget it. I'm not buying it.
Person 2: Wait! It's amazing! Unique, charming, drop dead gorgeous... Hello?







