There are other uses for scumbag troops. Split them into little groups with various kinds of attack orders on the flanks, and they can distract entire groups of enemies for at least a turn, or draw spells or missiles or whatever, which is often worth a few gold.
If you have a spell that makes use of dead units, then they can be nice twice.
Having a shield is usually better than no shield, but of course it costs resources.
PvK