This issue is sort of anti-dungeon master.
In dungeon master, the design was that you could learn almost everything you needed to know just by playing the game. You might make wrong guesses about the game, but the game would teach you itself.
For example, maybe you think that intelligence is the main stat of ninja skills. Then you gain a ninja level, and your dexterity goes up. Oho!
Maybe you think that there is no point in mana for a fighter, but later you realize everyone can cast spells, and then your 0 mana fighter fights an item that gives him a temporary pool of 5 mana points. Oho!
Basically you could get out of your mistakes and you could learn as you go.
In this game, we decide ahead of time how to allocate our statistics, and we will expect that dexterity is good for some class. However it's a "sufficiency" stat for people who fight hand to hand, not an "excel" stat. It helps them hit, but not to increase damage. It helps them to dodge, but mostly that won't work, and we should be avoiding damage through positioning anyway. Further, we're going to put dexterity on rogues in the back line, because that's the *longstanding* convention for what these stats are good for, and once we figure it out, we're going to be stuck.
I for one am now rolling my third party after having learned various things from the forum and game that weren't clear at the outset. This stuff should really all be in the manual. I'm not sure why it's so spartan. It shouldn't cost much to add pages to a PDF?