I have never done any scientific studies on the use of strobe as a defensive tool but from just some impromptu tests I have done on different friends, strobe would be useless with most lights. Yes it would surprise someone but it really isn't that hard to fight through it.
I had some friends over one night and we were looking at my lights and of course everyone was playing with the strobe modes because they are the coolest modes to non flashaholics. I decided to test the effectiveness of using strobe to disorient a person so I grabbed my Eagletac sx25l2t (1000 lumen, 81,500 lux @ 1m), set it to the alternating strobe mode, and had somebody run at me from about 20 feet. Everyone of them was able to run right at me and grab me. We did this four or five times with the same results. We tried it with the blue and green lenses with the same results. The only time we found it to be completely disorienting enough to do good was with the yellow lens. I'm not sure why but it was actually painful to look at with the yellow lens.
Yes you could say that strobe is effective based on what I said but only if you take into account the size of the light being used, the output, lux, and most importantly with a YELLOW lens and only then if it was shined directly into a person's eyes, if not directly into them it did ABSOLUTELY NOTHING. If the person was only glancing up to see where I was and then putting his head back down it had NO EFFECT.
As for a 200 lumen light doing any good it would only do good if you threw it and it hit them hard enough to knock em out. I did the same test with my Eagletac D25A2 (2xAA, 350 lumens, 3200 lux) and it did nothing, not even enough to justify shining it at them.
Overall from what I have learned from actually testing it, strobe is not worth staking your life on. A white strobe does nothing and even though the yellow was painful I wouldn't stake my life on it if somebody had a gun, knife, bat, etc. I might use it as a show of force before I draw my weapon but I would not use it as my sole defensive tool.
May I suggest you and your friend try the simple experiment I did and tell us whether you believe strobe is beneficial afterwards. If you do try it, remember to actually try and grab the other person, I bet if you set your mind to it and mentally block out the light you will be able to grab him. As long as you just run towards the light it isn't hard to do. What is hard is being the guy with light and trying to move around while keeping the light directly in the attackers eyes because I would be willing to bet that if someone is trying to actually attack you, you be moving. Most people would be moving and trying to avoid the attacker, not stand perfectly still and focus solely on shining it directly into the attacker's eyes.