I initially thought the trees in AH3 were overdone as well (biased because they kill my frame rate). But being OCD with too much time on my hands I went ahead and measured the tree density in AH3 and compared it to tree density of "real life", for the European terrain set. The tree density in AH3 is actually on the low side of the range in real life. (This is because there is almost no natural forests left, every tree has been cut down and whats left is a semi managed forest with higher tree density for economic purposes.)
A separate issue, of course, is the affect on GV game play. As Easyscor mentioned the people who attend the AvA Thursday Night Tank Fights have been adapting after first complaining that there's way too many trees. If after several months of GVing in forests people still have trouble finding each other to the point that it adversely affects game play, then maybe that would be the time to lobby HTC to cut some of them down.