Well well... Now I'm anxious to get this bike built just to see how comparably bad this group really is. Most of my friction shift experience is with Suntour Cyclone and Mountech, both which regularly perform well under heavy effort. According to many of the replies, I've effectively avoided experiencing poor derailleur performance because I've been using Suntour. It'll be interesting to see how much difference I notice.

And thanks to @3alarmer for his tips on how to build the group for optimal performance. I intend to follow his advice.