From e4, a DA can reach e6 (even if there is something on e5), g4, e2, or c4, using the D move, or c6 (even if d5 is occupied), g6, g2, or c2, using the A move.
Notice that a DA can never get to 48 of the 64 squares on the board: there are four different "colors" of DA.
Logically, a DA should be about as strong as a Knight except for its weakness of not being able to reach so many squares. Because its coverage of the board is so spotty, one expects it to be quite a bit weaker than the N.
In practice, the DA is of course noticeably weaker than the N, but because one of the squares it can reach is e5 or d5 (a center square, in other words), it's not as weak as you might think.
It would be possible to have a D7A7 piece which would be to the DA what the Rook is to the W. This DA-rider piece could go from a1 to a3, and if a3 was empty it could continue its move to a5, and if a5 empty, and so on; likewise from a1 to c3, et cetera. Because a D7A7 would already attack an enemy pawn without the need for any developing move, I do not yet use it in any of my games.