I've not made this blanket but size 11 needles seem rather big to me. I would try a smaller needle and swatch to see if I like it better. The pattern doesn't give a gauge that I can find and that's not really helpful.
Cheating is an option. . . . Cheaters never win and winners never cheat, but smart knitters who want to retain an iota of sanity do, cheerfully. ~~Kory Stamper