Right. I've played multiple tabletop games in the past. D&D, Pokémon TTA, etc. For HP or MP, each one uses a specific formula that utilizes a certain stat with no randomization involved. Trust me...in a proper tabletop, there'll be plenty of randomization to screw people over. xP It's good to give the players some certainty in how their characters will at least start. Just because it's a tabletop doesn't mean you should use dice rolls for everything. xD

...And actually, most don't even use an MP system. They usually use go by a Frequency system. At-Wills can be used one after another, Dailies can only be used once per in-game day, Battle means once per battle, etc. But of course, since digimon use MP in their games, using MP probably makes more sense here.