yes, kill all regular monsters but burn your land CD as soon as its available, so, army can fight to take seconds off. when you seen unique big monster then run off to get that unique monster out of your screen to let army cool down then go back and let army fight that unique monster cuz army cant kill it right away which is army can do SO much hit to take seconds off. then repeat as you go which you needed for your quest. I hope you can understand this. good luck!
Equip the life from death passive and equip reapers wrap. Then set your mages to the rune where they apply poison. They will no longer move or shoot, so just throw them behind you and let your skeletons kill everything. Get life globes to replenish your mana while continuously throwing mages behind you. Should have no problems.