+1
Additionally, if you have a measure/bar made, you can lasso the notes in PRV and hold Ctrl down, then drag to where you want a duplicate made. Or right click on what you have made in the track view, convert to a groove clip and then drag the right edge to make duplicates. You need to convert back to clips to edit again though.
Another thing you may want to look into is the Step Sequencer. You can make patterns in that, convert to groove clips and extend it out (right drag the edge) as many bars as you wish. The Step Sequencer also allows you to set randomness to the notes so they do not sound "robotic," and may be helpful for what you are describing. Try a YouTube search for "Step Sequencer in SONAR."
I have not run across a way to copy/paste just velocity... however, there is a nice tool called "Control Grouping" which is pretty universal in X3... select what you want to modify (Ctrl-left click all items, or it you can lasso them even better)... then hold the Ctrl key and change a parameter on one... that change will affect everything you selected.