I came across an article recently that recommended load testing with "1-shot" each at different powder charges.

As an example, 243 Winchester, 80gr Sierra BTSP H414

Load one each at: 43.0, 43.2, 43.4, 43.6, 43.8, 44.0, 44.2, 44.4, 44.6, 44.8 and 45.

This would be repeated with 3-5 different powders and groups would determine which powder would be best for that cartridge, bullet and rifle. Some groups would be tight and others more akin to a shotgun blast.

Has anyone tried this?

Do a search on the "Audette Methiod" AKA the "Ladder Meathiod"of load development. There is also a cut down version that has been talked about on this forum "OCW" (Optimual Charge Weight).
The idea of these is to find the best powder charge for a given combination in the fewest number of shots fired. As the powder charge increases, the impact point will string out (normaly in a upward direction). You look for the 3 charge weights that group the tightest along this string, and use the middle one, as it will tend to be the most forgiving of slight variances in powder charge and temprature. Thats the theory anyway. Me, I'm a 5 round per powder charge kind of guy.

If we're on the same page here, I think what is intended is firing one shot at each powder level and plotting where each shot landed on a graph. At a certain point(s) in the ladder, the shots will tend to cluster. The loads that produced the clusters will be where your research should start as to which is the exact best load. When I do this, I use wider steps between loads and after I have determined where the cluster falls, I go to smaller steps. Using my 22-250 for instance, a .2 gr step in the ladder would only produce a growing hole that would make it hard to plot the shots.

I read about the "OCW" method on another website, what I stated above appeared to be a different method altogether. I could be mistaken though.

That method could be pretty confusing without a very good shooter and a very accurate rifle. I have read about benchrest competitors who evaluate barrels with a dozen rounds or so...perhaps this is the type of method some of them might use.