If I remember correctly there wasnt any plane in earlier stages (but my memory might be flawed). The addition of the plane seems like a small afterthought just to give LOS since once the vehicle is out of LOS, the mark is usless. I think its a good thing that the mark stays there. I think it should stay as is. As Blovski wrote, it makes other strats more viable. Also, it is doctrinal, maybe a no-brainer to choose, but still a choice. And not all players go for it.
If you find your opponent go for alot of AT, use infantry or some sort of arty. German armor isnt the answer to everything.
Think its quite ok with the recent patch actually. Even if it lingers for a long time, it doesnt kill squads. Also its also a good AA target if you bother with tier 3.
Played this game in total over 200 hrs, and I wouldnt play that much if I didnt like it. Really enjoy this game, and like it better than coh1. Think relic has patched in a good pace this far. Some features still missing, but I am confident many of those features will be in the game sooner or later.