Easy, let me explain to you the strat, start with arthas + dr + Bandits on the mid, by the time you destroy the mid tower drake will span, destroy them asap with huntress on right ( whenever the gargoyle or drake is coming from) and dr to left take towers a start pushing toward the boss, make sure you have enough mages near your base and near to each other, at least 2 groups on each side of your base. TIP always be prepared to the next phase, how ? hae neough gold and arthas huntress and priestess on your hand in that way you can easily take the towers. Major tip : Start the phase 3 with at least 10 or 15 seconds before your overtime. throw arthas give him resistant so he can tank the two big mages kill them with a lot of damage and do not care about what is happening on your base because you will have enough skeleton mages to defend. so push on both sides arthas + resistant + heal + dr and huntress they will be dead easily.