Are low-armor and low-HP units useful at all when going for no losses?

[IntelCoreDuo]

Hello, I am trying to avoid losses totally, until I get 50 no-loss matches. After that, I'll avoid any losses for all units that are not in endless supply.

Does that mean that the vast majority of units are pretty useless for most fights? I would like to use huge stacks of low-leadership units to deal loads of damage, but it appears that they die very quickly. As a warrior I can't just resurrect them, and I would rather not use all my slots on paladins.

What are the ways to keep potential damage-yielding, weak units from dying?
I imagine that you could defend units by keeping them well behind my lines, maybe behind a dragon wall, if they are archer types.

For weaker melee units, Could Target force the enemy to attack a tank instead of the weaklings?

Also, can Sacrifice be used on summoned creatures? (That would, of course, render them useless.)

In general, do you use low health/defense units at all when avoiding losses? How do you deal with this?