First of all, you will need your troops to be able to survive 1 hit each from world boss. meaning your troops hp must be more than 10k to be able to do that and 14k hp to be able to survive a crit from world boss. To do this, you will need either knight or angel at lvl 30 and above. If your troops still couldn't survive 1 hit from the world boss, you need to increase your troop count by either equipping gems, Astral, guild skills or technology. I personally would not recommend equipping a charisma astral but do it if you have to. If your troops can survive 1 hit each from world boss, that's already 4 hit all together just to kill off your troops.