Enchant is never rendered useless. Untouchable virtually demands they either have extreme burst damage or magic immunity. Her heal is really good at healing one target, but sucks at healing multiple targets because the spirits' movement/AI/whatever sucks.
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So? Why does that matter? They're still those heroes' primary source of damage. Silencer and OD are basically worthless against BKBs. Silencer can still silence them with ulti, but carries generally don't care about that anyway.