I guess it boils down to what are the defining qualities for the hero? For War Machine, we know that he is using Stark's armor, so that is not stealing from Iron Man. But for Black Widow, her more typical common classic attributes are: red hair, black body suit showing cleavage, Widow bites - wrist bracelets, the red "Black Widow" hourglass symbol on her suit, and some of these attributes are missing in this IW version. They have been replaced by attributes associated with another character - Mockingbird: blonde hair, bodysuit without logo, using batons as her main weapon. While this is obviously still Black Widow, the lines are definitely blurred between these 2 characters solely on appearance.
If you chalk it up to character development, I can buy that, but as someone pointed out, this is not the classic Black Widow look that we are familiar with since IM2. And CW actually had the best classic BW look and best classic look HT BW figure. I'm still getting this IW BW...