The watercress is too strong a green for the dressing and the rest of the salad and it overpowered the rest. I would try it again with baby watercress, it might be better then.
Watercress & Endive Salad
From EatingWell: July/August 2008
Watercress and Belgian endive are topped with fresh corn kernels, grated egg and a simple lemon vinaigrette for a stunning first-course salad.