Bullseye is an excellent tool for SD or any other pistol/revolver shooting.
I don't care what you shoot, the goal is to hit your target, not see how many rounds you can put down range.
It's about fundamentals, Bullseye, more then anything else (excluding ISU pistol shooting) gives you those fundamentals.
A quote from MG Julian Hatcher, "Textbook of Pistols and Revolvers" 1935
Many practical users of pistols or revolvers are fond of making fun of target shooting, and the advice given on how to learn this branch of the sport. Such an attitude is will understood by the psychologist. It is founded in the unconscious jealousy and feeling of inferiority that the poor shot feels when he sees a well trained marksman making scores out of his power to equal. Unconsciously he will try to belittle that accomplishment that he does not possess, so that he will seem to his audience to be just as important and well equipped as the good marksman whom he reticules.
I've been around pistol/revolver shooters a long time, practical, target, SD, Military, and Law Enforcement. 40 years give or take.
As to the above quote, I've found no truer words have been spoken when it comes to pistol shooting.
I'm not that much of a pistol shooter, but I had one guy on my NG Pistol team that shot for the All Guard International team who I use to prove the point of fundamentals taught by Bullseye.
I don't know who here has had much to do with ISU or international pistol competition. In the rapid fire events you shoot 25 meters at a target similar to the police B-17. You have an oval 10 ring that's quite small.
You face the targets with your pistol in one hand, you have five targets. Its fired in three stages. Stage 1, the targets turn and from the pistol pointed at 45 degrees down, you raise the pistol and fire at the 5 targets in 7 seconds. Stage 2 is the same thing in 5 seconds, Stage three is fired in 3 seconds.
When in LE, military combat, or practical shooting when I get the "bullseye is useless-and a deterrent to good practical shooting" crowd I bring my pistol shooter to the course. Let me tell you, the practical shooter is humbled.
I'm not saying shoot Bullseye exclusively, I'm saying incorporate it in you training program. You need bullseye to ingrain the fundamentals into what is called muscle memory. Then it carries forward to your practical or SD shooting.
In practice use your SD pistol/revolver in your Bullseye shooting. Try shooting a pistol NM Course with your snub nose revolver. Your scores are gonna suck, but you'll learn to shoot your revolver.