Hehe, I didn’t mean it like the net’s bonus gets smaller as you have more games under your belt :) It’s just more difficult to get into a Jagdtiger after playing for a day than after playing for a year. :)
When you are starting to play, you are driving smaller tanks (better base camo) and your enemies have smaller view range and most likely no binocs.
Then you played for awhile and you are sitting in a huge ass 3 meters tall Jagdpanther and fully skilled and equipped enemy Pattons can see you from much father away.
According to World of Tanks Wiki, a Camouflage Net provides “+25% to the tank’s camouflage factor when the tank hull is stationary for 3 seconds.”
Of course, if a vehicle is going to be constantly moving a Camouflage Net is useless. But since a tank destroyer, self-propelled gun, or passive scout depends on remaining hidden in order to survive as long as possible, the +25% to its camouflage factor could very well be the deciding factor in its survival. The same principle is true for a tank down to 5% health that is attempting to become as invisible as it can.
Now, that page you linked to has a link to a table. Look at it, set “Shooting” to True and play with the “Camo Net?” value. Having the net on Ferdi, gives you extra 4 meters of “hiding range”. On ISU or JagdPanther, it’s 6 meters. That’s less than the tank’s length.
That’s the beauty of WoT descriptions, where most of the time things are much different in reality than what’s in the tooltip.
Now set the “Regular bush within 15 m” to 1, leave “Shooting” at False. And play with the net. Most low level TD’s are not visible until 50 meters REGARDLESS of the net. 50 meters is when the x-ray vision kicks in. For higher level TD’s, the net adds about 20 meters but, really, if you let the enemy to get within 75 meters of you without shooting at him, you have bigger problems than the extra 20 meters can solve. And the moment you start shooting, they see you regardless of the net.
Set the “Regular bush outside of 15 m” to 1 (so you are behind two bushes), set Shooting to True - again all the net gives you is 2-4 meters.
And I mentioned passive scouting and arty as being the best usage of the net. That’s because they don’t shoot when the enemies are around. And when they do, they usually die.
Of course, there are extremely rare situations when a net can be useful on a TD or, God forbid, a heavy tank but 99% of the time the only thing it provides is a false sense of security.
[edit] To add some pratical advice to all the theorycraft above, if, in a TD (or any other tank really), you want to shoot at enemies without them shooting back at you, never just park in a bush. Use double bush (the farther bush should be beyond 15 meters from you) or, better yet, use hard cover, like rocks and buildings, hide there when reloading, pop out for a quick shot and then hide again. Having a bush right beside a rock is great, it allows you to sit there and wait for them but once you shoot, always assume they see you and hide behind a rock. Arty especially loves TDs who think no one can see them in a bush.
Oh and remember that you can’t see anyone from behind a double bush either, never use them when there is no one to spot for you.