FletcherD,
The answer to your question regarding whether you are wasting your time with rifle loads is "no". Until you try something you really don't know what you're gonna get. The latest Hornady manual has some good info on rifle cartridges in T/C Encore barrels.
Even the "Light Magnum" loads from Hornady, and others, will give an increase in velocity even in the short pistol barrels.
Yooper77, I am not suprised at the results you got regarding IMR-4064 vs. IMR-4350. I got similar results in my 30-06 JDJ as well. The IMR-4064 gave me nearly 100 fps faster MV when compared to H-4350, with virtually the same accuracy.
Again, I re-iterate, generally speaking, the same powders that give the best rifle ballistics typically give the best pistol ballistics, with some exceptions. Pistol barrrels do not, as a general rule, require faster powders to give the best results. You and both have listed some of the exceptions.
Based on data generated by different powder and bullet companies, I think that RL19 would be an excellent choice in 7-08, in terms of external ballistics. I've got a 7-08 bbl that I will be trying soon, so I may soon find out.