I don'y know about metal drums or any other drum machine than AD2, but a coupe of things come to mind that I know AD2 is good at.
Regards messing around with velocities. AD2 has a Beat Transform function for manipulating velocities that's extremely intuitive helps dial in the dynamics very well. It works with the internal midi parts, or you can just drag your own in from the midi track. It breaks the kits into parts, so all snares are grouped together, hat's together etc. so you can adjust these against each other, and get the tone you are after through velcities. You can also push and pull the accents for 8ths and 16ths, ad et the velocity dynamic range as a whole. Then drag the part back ou to the midi track. It's really worth messing with to get potential it provides.
Additionally, if you then want to separate the parts out as yo can with the CAL suggestion above. Before dragging back out to the midi track, you can mute by group. and just rag out the unmuted group to the idi track. So it you want to use just a snare group from another sample player, you mute everything but the snare, nd drag the snare to one midi track, and then mute just the snare and drag that to another track. So easy to separate the parts up this way.
All though AD mainly replicates realistic kits, I know the DnB programmers use AD2 a lot, because of it's envelopes on the raw samples. The tools to change the shape of before and geting them punchy and short for fast playing, may transfer to metal programming well.