Glad to get this resolved finally.
It turns out that what is keeping the banding heroes out of battle is not ECs (because there aren't any in play), but is actually the field of battle itself. HHI is protecting the field of battle from having banding heroes enter it. Therefore, HHI protects the "field of battle" in the same way that RTC protects "Jacob" from ECs of a certain brigade from blocking him. Therefore, we end up with this:
Jacob + Reuben's Torn Clothes
SA source = enhancement
card/place whose protection keeps ignored cards out of battle = Jacob
target card = chosen evil brigade ECs
if Jacob is eliminated, then chosen evil brigade can block again
HHI
SA source = artifact
card/place whose protection keeps ignored cards out of battle = field of battle
target card = all banding heroes
since the field of battle CAN'T be eliminated, banding heroes can NEVER enter battle