Tis' the plight of Horizontal Roughing.
The more complex the part, the more random jumping around it's going to do.
If you just want straight letters with a single cut line for each (no pocketing), you can just bring them in from Rhino as open curves, and then use profiling. The trick is to set your stock offset as a negative number equal to half the diameter of your cutter. Then the cutter goes right down the center of the line.
If you want fancier stuff (pocketing), the best way I've found is to profile them with multiple stepovers. Setting it to "depth first" will limit the jumping around some. Sometimes the stepovers will cut into inside stuff that has to stay, like on a brush font lower case "g", or "o", but leave uncut portions elsewhere. Limit the stepover to prevent the offending move and then draw a polyine to create a toolpath that fills gaps.