I know that mission well. You can grenade the radiators on the giant tank easier than you can hit them with lancer shots.
For reasons that continue to escape me, Sega redirected the Valkyria sequels to the PSP, the last of which didn't even get an English localization. As you'd no doubt expect, the loss of all that hardware muscle meant that PSP versions were mere shadows of the PS3 original.
Last I heard, the franchise is now in social/mobile territory. A boon in Asia I suppose, but certainly not helping the fans over here.
In Sega's defence however, they're in no shape right now to bankroll much else.