I cannot describe how much of a disappointment this game is. I knew it would be rough going in, but the number of floors of what amounts to the same dungeon is just staggering. Even if you just complete the main game, it still has to be something like 1,000 floors, not including the Ancient Cave (which requires more than one play through to fully beat). To top it all off, the Ancient Cave is much better to tackle on a new game+. I managed to beat this game, and then rage sold it on eBay.
I feel like there was no play testing or QA here. There are so many typos in the script (in addition to the usual localization cheese), so many bugs, and it's not fun to play that it could have never passed QA.
My understanding is that this game was originally slated for PSX, but went through development hell before landing on GBC. It's one good idea (the grid combat) is so poorly balanced, like they had the idea but no details on how to make it work. There is just so much gross stuff here that needs to be cleaned up. You didn't mention the menu in your review--even by the end of the game, I still found it to be a cluster to navigate. There was some interesting concepts here and in Lufia II, but it's like the planners just ignored all those things in favor of this procedural dungeon nonsense.
I've thought about reviewing this game just to rip it to shreds, but you did that enough here that I'm satisfied.