Cyclops are weak units. I think the weakest 5 level ones.
Only good thing is their high damage resistance but they deal only a little damage and are slow. You also cannot heal them
I would not take third 5 level unit to the army. You will not be able to keep stoneskin on all of them and it will be harder to keep them alive by healing all of them.
You also cannot resurrect them so a good 4 level unit will be a better choice (the best choice will be some summoning unit like demonologists)