Troops do not add or detract from blood hunting, only the commander is used.

If you have 3 Blood-3 w/SDR's hunting that probably means you are getting in too many slaves for the population. Try splitting one of your hunters to another 5k+ province with another hunter and drop your taxes and you should be okay, you'll get unrest but it should even out depending on if you get a 'big haul' of slaves or a gutterball.