Some games use those secondary stats to be more of a direct impact than how base stats work. For example, having a cap on stats. If a cap on MND/STR/whatever is reached, that's where the secondary stat comes in. It may not have additional attributes to it (like DEX increases dmg (for ARC) AND increases crit), but it does affect your performance in a direct way. Another example would be differently scaled multipliers, as some others have indicated.

Quote Originally Posted by Naunet View Post
I suppose the argument could be made that we need both because they scale differently, yea.

Though truth be told, in response to a point you made earlier in your post, I really don't find the different +potency stats (mnd, str, dex, int) all that engaging. They all do exactly the same thing conceptually, with the distinction they supposedly bring already handled by the disciple/class/job restrictions on gear. You're not going to ever see a WHM wearing +STR gear not because they're actively choosing to avoid STR on their gear but because it's completely unavailable to them. You might call out the attribute points we get as a moment of choice, but... it's not and I really wish Squeenix had designed something more game changing than just "yay spend points in your main stat!"

So yea, in that case, I'm all for rolling mind, strength, dexterity, and intelligence into a single stat and cutting some of the unnecessary stat bloat. Ideally Squeenix would replace it with compelling choices to make regarding modifications to abilities.
Not really sure what you would realistically consider them doing on revolutionizing stats. The only things that came to mind as to what you meant were to either combine everyone's separated stats into one singular stat that everyone would need (i.e. an "output" stat) or to create stats that directly affect only specific abilities/spells. That second one being WAY too complex and pretty much useless. If that were what you intended, have you ever played FFXI? All the gear swapping would pretty much be increased to everything you did, rather than 90% of it lol. Although that system wouldn't work in general given we can't gear swap mid-fight lol.