Heliborne assault viable in conventional high intensity conflict

The heliborne assault was pioneered in the 1960s and has been used since in operations to great effect – in Vietnam (as shown in great “We Were Soldiers” movie), Operation Rhodes in 1970 War of Attrition, Indian operations in Sri Lanka and wars in Africa (Rhodesian K-CAR ops, Portuguese forces in Angola etc.

However most of these ops were in counter insurgency operations or at least against foes without much in the way of air defence.

Against massed choppers even such primitive systems as manually trained 14.5mm/12.7mm machine guns can be effective let alone AAA and MANPADS.

So is heliborne assault viable in a conventional high intensity conflict with large amounts of air defence present, or is it primarily a special forces/raiding type operation better suited for COIN or poorly defended sectors or for initial surprise assaults?

Indeed even in COIN the results can be disastrous as is the example of the destruction of 38th DR Afghanistan Brigade and loss of 24 helicopters at 2nd Battle of Zhawar in 1986.