I think your right on the money. I bought a 314-2 over a year ago and it was a hassle at best. This year I decided to try it again because I was having trouble adjusting for follow shots with side english. Now follow shots are fairly simple but draw is a pain. I over cut long slow draw shots with side. Keeping the cue more level helps, speed helps and using less side helps. Overall I'm starting to like it more but I have to remember to adjust.
With a reg shaft squirt and swerve balance each other out. If I let up on a side english draw stroke with a reg shaft I may still make the ball. With the pred I'm sure to over cut the hell out of it. Playing one hole it has advantages but I need more time to adjust for slow speed spin shots as you noted. The one thing I miss is my fatter shaft with a conical taper. It way more solid and comfortable. I like the fuller feeling in my fingers.
Another thing to note is equipment and conditions. Older worn ball sets seem to curve more. I think is more table friction due to condition of the balls. More friction, more swerve etc. Of course older dirty cloth adds more friction as well. I mean cloth can only handle the oil from so many cheeseburgers and fries. LOL
I think the OP needs to find the real reason for missed shots. We all miss shots but most good players know why. If you don't know why then you don't know what to correct. Usually it stroke mechanics or you moved on the shot or your alignment needs work, no matter what shaft you use.
Rod
I concur w/your additional info about conditions playing a big role in the outcome
