The front delts are used as a stabilization factor, but not a major factor when doing BB curls. All three heads of the delts, traps, upper/lower back, pec's, abs, etc act as a unit. There are all part of the whole when curling. The triceps are the main counter/balance/stabilization function when curling (if a numbing agent were applied to the 3 headed triceps, to deaden their muscle function...you would have a hard time curling anything). Why the front (anterior) delts would be "burned out" before for the biceps defies logic. If this happens, that the front delts "burns out", than that person has not a clue how to workout or understand how the human body works..
If doing standing BB curls, bend slightly(4 to 6 inches) forward from the waist and curl that way for a better affect on the biceps. Also quite a few men, with very large biceps, do not do full ROM's at all. Their rep range is in the middle ROM for any set. Keeping the time under tension (TUT) on the biceps themselves. May not be for everyone, but works very well for them. Good Luck.