[MaxWilson]

Nope. The mage will cast where he thinks it's best, which is usually on low-Prot units close to the mage. For good coverage, it's best to have multiple mages casting Legions of Steel, spread out through your army. It may also be necessary to station your mages/weak troops closer to the heavy inf than you'd prefer (use an archer decoy). If a mage casts it on the wrong target, vindictively order him to assault an enemy strongpoint alone as punishment. For what it's worth, Strength of Giants is usually targetted a little more intelligently than Legions of Steel, perhaps because it has slightly more range.

Sermon of Courage raises Morale by +2 for the whole battle, for those units.

Legions of Steel is not cumulative with itself on the same troops, but it does last the whole battle, as do all other troop buffs that don't have an explicit ending condition (e.g. Mistform has a 1% chance of wearing off per hit, BEs end when the caster dies).

-Max