Sue brings up a good point. There's a time to pound out the miles, there's a time to hammer it with the speed. Without a balance of both, your race performances will stagnate.
I wouldn't worry about the paces of those long runs. Look at what you said you were doing last year. The first 11 of a 22 miler around 30-45 seconds slower than marathon pace, the final 11 at or faster than marathon pace. That's a lot of pace for a long run, you don't need that much in that run. Also, don't discount the humidity. It's been beating me to a pulp. I know things will come around hopefully soon as the cool, crisp fall days settle in. The same will happen for you.