And I still don't understand how a bundle of concussion grenades can damage a tank.
To be fair, pretty much every infantry AT weapon is going to be overpowered in some respects. Until the fausts/bazookas/schrecks etc, most of the AT weapons would be pretty piss poor and either difficult to use or unlikely to do more than damage a tank. The AT rifles in particular are bad in this respect. They would almost never outright destroy a tank irl, but they could often damage one. And since it's pretty impossible to model such damage in BF2, either we have unrealistically overpowered AT weapons... or in early maps tanks are gods striding the battlefield. I think the latter would put many people off playing.
I have to admit, it does get to me how blatantly unrealistic AT weapons are. With AT grenades and satchels of high explosives seemingly being nukes.... but with such engine limitations you have to do the best you can.