I'd definitely say that harmonizer doubler's are a total waste of time. They don't even begin to approach what TOTL studio doublers do, and make the voice sound artificial and phasey.

The less you use the VH, the more effective it is. One voice above (not doubled) is usually all you need (and what you would usually do live, in a band) at most one above, one below for a tenor, two above for a baritone or basso...

Try to think in real band terms, and you usually get something far more realistic...