I just listened to the podcast and... I really hope James doesn't put too much emphasis on 4 Heroes of Light being super hard and "you'll die over and over at first" in his review.
Johnny's question was very much relevant: you must have been playing it wrong, James. I'm not as far into the game as you are, but I did complete a few dungeons, and I've yet to have had my party wiped out.
My only theory as to what you did wrong would be that you didn't make full use of your spells at first. Limited SP/MP/whatev in JRPGs have conditioned us to rely on magic only as a last resort, but in this game you are encouraged to use it at all times, since your AP replenish automatically, and are therefore an infinite resource.
You get the Cure spell very early in the game, so there's little excuse to not have near-full HP at the end of every battle.
The "strategy" that hasn't failed me once so far is to thin out the enemies until there's one left, preferably low on health, and then use Boost and Cure before landing the final blow, so as to start the next battle fully prepared.
I haven't had to grind yet. Game's really not that hard. And any JRPG that encourages you to use the magic system as much as possible instead of having you make your dark mage attack with his staff for 3 points of damage in most battles, saving your MP for an eventual boss, should be praised for it.