I have found one exception to what you said. Camo on my Lowe. When I first heard about it I scoffed at it but then I saw some Lowes blinking out fairly quick in my battles. At first I thought it was the invisi bug we sometimes run into in this game but after speaking to other Lowe players who run camo I found out its them running camo. Camo on the Lowe only works in certain situations though. Namely the medium and long ranges. So I tried it on my Lowe since my crew already had all the other important skills I wanted.Repair is never a bad thing for a heavy. Camo is always bad for a heavy (can't hide it anyway). Anything that increases speed might be good too.
In my experience I found a camo net and 100% camo crew skill has helped me getting detected less frequently and once detected allows my tank to disappear off the enemy's sight faster. Again this only works at medium ranges or longer. This works in the Lowe's favor when used in a sniper role which is what I mainly use mine for. I will admit though there are more important skills to get for a Lowe. Like BIA, Repair, Fire, etc., but if you already have all that adding camo does offer some help in certain situations.
I've heard of Tiger I players doing this as well but I have never tried it on a Tiger I so cant say how well, if at all, it works. I have talked to a couple Tiger I players that swear by it though.