I definitely agree. If you pick up book 12 without reading the previous 11 you're going to have no idea what is going on. You'll have no idea who any of the characters are or why they are doing the things that they are doing, or even the significance of what they are doing. you'll have no idea about what their personalities are like or their motivations for doing what they do, or have no idea what their quirks are or where they came from. You'll hve no idea what's going on, why certain events are significant, why certain people are doing certain things. You'd probably read about two pages and say WTF then set it down and never touch it again.
like publius75 I too had to keep flipping to the glossary while reading the first book or three to figure out what all the terminology meant, and how to even pronounce some of the character's names correctly. Robert Jordan explains it, and at the same time doesn't quite explain it sometimes, and he's made up so many words and names and terms and things it's hard to keep them all straight at first.
I understand your dislike for long winded overly descriptive writing, and it WoT does tend to drag in certain places, or around certain characters you wish would meet with a horrible accident so you can get back to the part of the story that's more entertaining, *cough*Elayne*cough* but if you don't read the foundation for the climax of the series it'll be meaningless to you. It's not like it's going to be a completely different story independant of the first 11 books, Brandon is doing his best to make it so that you can't tell a difference between the writing style in his parts of the ending from Robert Jordan's. He's trying to stay true to Robert Jordan's vision and style, rather than hijacking the series with his own.
One thing I've found that helps with reading the Wheel of Time if you're really set on reading these last three books because they're being worked on by Brandon Sanderson, would be to get the audiobooks from the library and listen to them. It doesn't take as much effort and you can probably find them abridged too. That way you get caught up on the story without actually having to put in the effort to read it yourself. I have the whole series loaded on my Ipod and I listened to the whole thing in preparation of the next one coming out to refamiliarize myself with the characters the plots and the subplots while I was at work. no extra time taken out of my day, and I got entertained while doing one of the dullest jobs in the universe (mailman).