So, in Dragon Quest typically using spells misses, or is less efficient that physical attacks AND wastes lots of MP. And I should be blamed for using only Fight and not use Spells when they are pure crap ? I'd rather blame Enix for not including efficient spells in their games (healing and escape being the only really useful spells of all DQ games, ever).
Spells don't 'typically miss' in DQ games. Some may do very little damage (if you cast Blaze on a fire enemy, in some games it'll do like 1 damage, in others it'll heal the enemy). The only other time a spell may fail is if you try and use certain defensive or status affecting spells on a boss. Silence spells typically fail on bosses for example. General field battles have a very low failure rate. You just need to assess the situation and choose a spell that makes sense. HINT: If you're near a volcano, fire spells probably aren't your most potent weapon.
MP balance is another case entirely, but DQ games are generally balanced fairly well unless you're spamming a group spell over and over again. If you're planning your battles well, MP lasts a very long time.
DQ games really starting with the SNES DQ6 have skills that cost little or no mp that are also equally effective if you use them wisely.
If healing and escape spells are the only spells you use, you're one of the people spamming the fight command. At the very least you should consider using some attack/defense boost spells (or spells that lower the same stats of your enemies). Some enemies in the field in DQ games have very high defense and the only way to quickly dispatch them without grinding your level up is a sap spell to drain their defense.