Replace Yosemite's DNS discoveryd with the former mDNSResponder.

mdnsresponder.sh

#!/bin/bash

if [ ! $(whoami) = 'root' ]; then
	echo "This script should be run as root." > /dev/stderr
	exit 1
fi

spinner()
{
    local pid=$!
    local delay=0.75
    local spinstr='|/-\'
    local text=$1
    local count=0
    
    echo -ne "$text "
    while [ "$(ps a | awk '{print $1}' | grep $pid)" ]; do
        local temp=${spinstr#?}
        printf "[%c]" "$spinstr"
        local spinstr=$temp${spinstr%"$temp"}
        sleep $delay
        printf "\b\b\b"
    done
    echo -ne "\b\b\b\n"
}

case "$1" in
	install)
		(cp ./mDNSResponder /usr/sbin/ && cp ./mDNSResponderHelper /usr/sbin/ && cp ./com.apple.mDNSResponder.plist /System/Library/LaunchDaemons/ && cp ./com.apple.mDNSResponderHelper.plist /System/Library/LaunchDaemons/) > /dev/null 2>&1 & spinner "copying required files"
		
		(launchctl unload -w /System/Library/LaunchDaemons/com.apple.discoveryd.plist && launchctl unload -w /System/Library/LaunchDaemons/com.apple.discoveryd_helper.plist) > /dev/null 2>&1 & spinner "deactivating discoveryd"
		
		(launchctl load -w /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist && launchctl load -w /System/Library/LaunchDaemons/com.apple.mDNSResponderHelper.plist) > /dev/null 2>&1 & spinner "activating mDNSResponder"
		
		echo -e "Please reboot your machine"
		;;
	remove)
		(launchctl unload -w /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist && launchctl unload -w /System/Library/LaunchDaemons/com.apple.mDNSResponderHelper.plist) > /dev/null 2>&1 & spinner "deactivating mDNSResponder"
		
		(launchctl load -w /System/Library/LaunchDaemons/com.apple.discoveryd.plist && launchctl load -w /System/Library/LaunchDaemons/com.apple.discoveryd_helper.plist) > /dev/null 2>&1 & spinner "activating discoveryd"
		
		(rm -rf /usr/sbin/mDNSResponder && rm -rf /usr/sbin/mDNSResponderHelper && rm -rf /System/Library/LaunchDaemons/com.apple.mDNSResponder.plist && rm -rf /System/Library/LaunchDaemons/com.apple.mDNSResponderHelper.plist) > /dev/null 2>&1 & spinner "removing unnecessary files"
		
		echo -e "Please reboot your machine"
		;;
	*)
		echo -e "Usage: mdnsresponder.sh {install|remove}"
		exit 1
		;;
esac

usage.txt

Usage:
1. Download and unzip the archive from https://copy.com/DKXr6KxqL1LrFkpA into the same directory as the attached shell script
2. chmod +x ./mdnsresponder.sh
3. sudo ./mdnsresponder.sh install
4. reboot your machine

To switch back to discoverd:
1. sudo ./mdnsresponder.sh remove
2. reboot your machine

@dlueth yes link broken to download

THANKS A LOT! My internet connection only works on Chrome and not in Safari, Dropbox, Spotify... And you have resolved it!!!!!!!!!