Is it a good strategy to buy mutual funds where the NAV has come off sharply?

Again you are wrong in both the cases. Whether it is stocks or mutual funds, a sharp correction cannot be the only criterion for buying them. A sharp correction in NAV can be due to a variety of reasons. The fund may be facing redemption pressure. Alternatively, it may be exposed to the wrong industry or theme. For example tech funds that were launched in 2000 saw their NAV deplete by 80% in 1 year. That did not automatically make them a buying opportunity.