Bigger buildings are now much less vulnerable to rocket attacks

I've noticed that it is no longer possible to cause the collapse of a large building using rocket attacks in a single pass. I first noticed this a couple of weeks ago (I believe 1.8.0.10?) I would like to see that fixed, as rocket attacks by helicopters are now much less viable when the enemy is hiding in them, effectively creating bunkers.

Test scenario:

Set up helicopter with HEDP rounds
Make pass over admin building with pointed roof at military base levie and attack it with full salvo.

Current result: it takes up to three passes with 100% hit rate to level the building

Expected / past result: It takes only one pass with 100% hit rate or maybe two passes with ~75% hit rate to level the building and cause collapse

Test scenario:

Set up helicopter with HEDP rounds
Make pass over admin building with pointed roof at military base levie and attack it with full salvo.

Current result: it takes up to three passes with 100% hit rate to level the building

Expected / past result: It takes only one pass with 100% hit rate or maybe two passes with ~75% hit rate to level the building and cause collapse