That hasn't been my experience. This month, for example, my daily impressions are up about 30% and my CTR is up slightly compared to last month, but eCPM is running 34% higher.
My post-Smart Pricing eCPM is higher than my pre-Smart Pricing eCPM by several percentage points, and total revenues should hit a record this month. So I agree that Smart Pricing doesn't have to hurt publishers. Publishers who are being hurt by Smart Pricing (or by other, unknown factors) need to think about the reasons why that might be happening. One possibility is over-optimization that increases clickthroughs at the expense of conversions.
If unhappy publishers leave AdSense for greener pastures, that could actually help Google by increasing the overall quality of referral traffic to advertisers (thereby encouraging higher bids). Why? Because publishers who are being "smartpriced to death" (to borrow a term that we've seen on this forum) probably aren't delivering clicks that convert for advertisers.