I have used Javs for area fire on trenches before. I could not see the troops so I area fired the tench they were in. Out of 8 baddies I thnk 5 were killed outright with the rest breaking.
As mentioned before, if it saves some armor or a squad, it is worth the cost....
...Well as long as you have some to spare...i.e... either a stockpile somewhere linke in your LAV or you are pretty confident the armor is all gone.