I don't even remember I was too wide-eyed at the time-- I just managed to get a LOT of dark orbs lined up with DMeta's enhancement and Dark Flamie's enhancement. I mean, I noticed that Thanatos there couldn't deal enough damage to kill me so I decided to build up for a fun finale. Also, my DMeta didn't hit over 3mil-- that's a 2.460mil attack on mine (the DMeta friend's is like 20 levels higher than mine, yes a few hundred attack makes THAT much of a difference). But still, it's absurd.
DMeta changes how the game is played, honestly. Instead of being a game of comboing and getting the right matches, it becomes a strategic game of prediction and foresight and resource management. You have to be a few steps ahead of the game or you will either die (hello, glass cannon team) or overheal (which makes you absolutely useless and makes it so you have to take a hit and pray it's one you can survive). That's why I have Vamp and BadShynee in there instead of another hard-hitting attacker. Vamp can get rid of heart orbs and give me more ammo to clear enemies away, and BadShynee can change light orbs into emergency heart orbs (as well as 3000 HP), which can also be converted to dark for a final blow with DMeta's active and King Flamie's active. But even then you have to be careful not to overheal with BadShynee too.
The whole object of DMeta is to blast away weak enemies on early floors and prepare for the boss, since you have to 1) have a lot of dark orbs to enhance and do rows with, 2) have your HP below 80% BEFORE you get to the boss because 3) you only have a turn or two to prepare the first and final blow because if you DON'T overkill the boss you are almost guaranteed an instant game over.
So yeah, it's fun and all, but it's got its own challenge to it.