This is a problem with the latency of when the note is echoed back to you, which makes it feel slow. This is because Dorico doesn’t know when you first play the note on your MIDI keyboard whether the resulting pitch should be, based on the transposition of the instrument, so it has to wait until the note has been input before it can sound it back to you, and it sounds it with a fixed length rather than the length you actually held the key down for. This will be addressed in the next update, and I think it’ll make the program feel a lot faster.