mDNSResponder missing
mDNSResponder was replaced by DiscoveryUtil in Yosemite. So Bonjour is still enabled. According to this Apple-kb article you might have to download updated printer drivers from Apple or the original manufacturer or re-add your printer with a different set up.
If you still have problems discovering your printer an Apple-discussion-thread might help:  unblock discoveryd in the firewall preferences and an immediate reboot...