After many complaints from the developer community about poor networking performance on Yosemite, the latest beta of OS X 10.10.4 has dropped discoveryd in favor of the old process used by previous versions of the Mac operating system. This should address many of the network stability issues introduced with Yosemite and its new networking stack.
The discoveryd process has been subject to much criticism in recent months as it causes users to regularly drop WiFi access and causes network shares to list many times over, due to bugs. Many developers, such as Craig Hockenberry, have complained about the buggy software and workarounds have been found to include substituting the older system (called mDNSResponder) back into Yosemite.
discoveryd would cause random crashes, duplicate names on the network and many other WiFi-relate bugs. In the latest beta, Apple appears to have applied the same fix as the enthusiasts by axing discoveryd completely.