Grenade damage is balanced perfectly right now for playability. RO has come a long way from the mini-nukes of the Mod and RO1. Search the old RO fourms for pages and pages on the fight to reduce the blast radius.
This from an Aug 2011 join date. Most of us around who played RO1 from the start would beg to differ. The grenades being balanced for gameplay is not a good thing (if that is even true), and the so called "mini-nukes" of RO1 desperately need tocome back to preserve the realism of this game franchise.
Balace for gameplay and dumbing everything down is out there for you in a half a hundred other FPS arcadey shooters. I for one would like RO to stick to realism, even when that means it is harder for players to work together to overcome certain weapons because of the realistic effects of such. Those pages and pages talking about reducing damage....no, YOU go do a search and you'll notice those were either newer players who couldn't get their heads around the requirement for more communication, teamwork and THINKING about doing things differently rather than running up the same path a hundred times. The general "gist" of those threads are like this one....there are a few who come on complaining, and the players who have been around and play for a long time, or those who come with an open mind and adapt to the game, coming along saying the same thing....get used to the game, try new things, communicate...and after all that you still don't like it, maybe it's time to go back to many of the other games out there.
To the OP, yeah, given that the AT grenades are a shaped charge and essentially deliver their force into a small cone of spall into the tank there should still be a bit more of an effect if close to it. Not a terrible lto more and certainly not as much as a regular grenade but I also find it a bit low.