I can't for the life of me figure out how multiclassing spellcasters work.
So, a 3rd-level mage/3rd-level cleric...
* casts spells per day as a 6th-level character
* can prepare spells available to a 3rd-level wizard or to a 3rd-level cleric
As to the first, there is no such thing as casting as a 6th level character. There's a 6th level Mage. There's also a 6th level Cleric. But there's no "6th level character" casting progression. So does this person use the spells per day table of the Mage, the Cleric, or does he use both and get to nearly double his spells per day?
As to the second, is the word "or" intented as a mutual exclusive, or is it intended as a meaningless grammatical particle in a summation? Does the "prepare spells available to a 3rd level Mage" indicate a limitation on the maximum spell level (in this case, 2nd level spells), or does it also also determine the amount of spells (in this case, 1 + 3 = 4 spells prepared)?
Why is there a special subclass to "glue" a caster and a non-caster for the Ranger/Druid combination? Those are both spellcasting classes.
If I make a Fighter 9/Cleric 1, does this mean I get to prepare 2 Cleric spells per day (Cleric level + 1 = 2), but I do get the spell slots per day as a 10th level Cleric? So I can cast tons of Blesses and Cure Wounds with heightened spell slots per day, all for the steep, steep cost of a 1-level delay in obtaining Fighter class features? Because if that's the case I have some unfortunate news about that whole "prevent 1-level dip abuses" plan you had...
No really, how does this work? I know it's not the rules text and just a summarized preview but this is way too vague to make sense of.
Edit:
It just occurred to me that this system would make about a hundred times more sense if it was the opposite of what the article says. So instead of this:
* casts spells per day as a 6th-level character
* can prepare spells available to a 3rd-level wizard or to a 3rd-level cleric
It ought to be this:
* casts spells per day as a 3rd-level wizard and a 3rd-level cleric
* can prepare spells available to a 6th-level character
So this hypothetical character could prepare 7 spells in total (spellcasting levels + 1), but he'd have the 4/2 slots of a Mage as well as the 3/1 slots of a Cleric. Compared to the slots a pure 6th level Mage would have (4/3/3), this compares fairly nicely. No 3rd level spells, but in exchange he does get more 1st level spells, greater flexibility in choosing which spells he can choose, and the class features of both (more lores, Channel Divinity, both an attack bonus and a spellcasting bonus, etc.)