It sounds like your landscape architect did a great job of choosing low-maintenance perennials! But I agree, if you don't love the looks of something, definitely time to give it the boot. :) I think with the Karl Foerster and coneflower, maybe something low and yellow would look nice. What about some more coreopsis? Always great to repeat plants to give unity to the garden, and I think the yellow would be a nice compliment to the blooms of KF as well as the pink/purple of the coneflower. I will admit that I have at least seven varieties of coreopsis right now, so I'm obviously biased. :p Or maybe another smaller grass with a slightly different bloom than KF? Pennisetum Hameln might be nice if you have the room - they are a more rounded grass form, which would be a nice compliment to the spiky KF.

Well, since I live very close the lake and the metropark system, I am afraid that I will have to try some of these products and hope for the best. I have never had to worry about critters on such as consistent basis as I do in this yard. I grew accustomed to deer pruning my roses for me in the winter, but that was the worst I really dealt with in my previous home. My new yard is fenced completely, but smaller animals can get in on the side that is a picket fence and thanks to my SIL's dogs, there are a couple holes underneat the privacy fence for animals to creep under. (grrr!) I am leaving the motion light on to see if that helps, and I sprinked cayenne around the gardens today, so I will keep my fingers crossed for tonight.

Looks like aster yellows (phyto....) to me, except the link below says plants will show chlorosis. The leaf hoppers spread it, apparently. Compare the pictures in the link. Looks like that weird seed head. If you grew that stand in a year, I'd get rid of the plants, but save the good seed. Take a year off and maybe plant w/ a cover crop (not aster-related). Then put new plants in. And maybe spray to keep the leaf-hoppers off. Just a guess, but might work. Really nice looking plants you've got, but the disease is incurable and apparently will warp all the flowers. Good luck. Here is a link that might be useful: Aster yellows

Echinacea have a reputation for doing that when they are receiving too much water. And it only seems to affect the terminal, budded ends. We used to see it all the time at the nursery when the seasonal staff got over indulgent with the watering wands :-) Make sure they are planted in very well drained soil and maybe cut back on any irrigation.