Generally, still today DCC mode, aka "Easy mode" as it's called today allows for a more generous control of the trains much like a model railroad but as you noticed, AI driven and Cab control not so much. I have had AI get stuck on steep slopes and tight curves, forcing me to make changes in my operations and in some instances adjust the curvature on my old route where the tracks worked perfectly fine in older versions but don't do so well any longer.
John
Trainz User Since: 12-2003
Trainz User ID: 124863
Trainz-PLUS: 117669