no one can get on target at 600, you'll already have to know where he is. 
... and for that, you often don't need an icon at all. Tanks caught moving in the open will still be bomb magnets and have a short life span, though maybe a little longer than today. But tanks hiding from planes will be much more difficult to spot (short icon ranges and loss of icon when under trees/in barns). If that really happens, it seems more "realistic" to me in the end.
At best, more cooperation between tankbusters, spotters and units on the ground will be required. If that would happen, it would be great. But we really have to wait how it all plays out. So give the changes one or two weeks to settle down...