first of all harvester is not that op look it this way that 1 creature costing 300 power so you rush tier 2 thats 150 power you need to wait 300 power doing nathing (spawning nathing) in orther to use him in pvp while enemy is creating tons of new tactics that can bring your harvester down and not only that when he do so you spen 300 power for nathing + while having him you need to have some other supp for him or your self cause he wont last long alone hes good but only if you have good advantage and know the time when to use him.