I know what you're referring to. Hip dumpers. All for show.
I don't like to think of that as over-angulating.
To me, angulating is leaning out with the upper body to counter balance any inclination that is happening at the same time. Dumping the hip in does result in an appearance that is similar to angulation if they attempt to maintain an upright torso with shoulders level, the common advice given, but its only form and not function.
Yes they end up too much inside, which is the exact opposite of what angulation is supposed to acheive. The problem is not over-angulation, its over-inclination. In fact in order to overcome the extreme amount of inclination they are going for by dumping their hip inside, they would need to angulate even more to stay off the inside ski. see?
What to do with them? Its not a quick fix.
Work on progressive movements and progressive turn entries, get them to linger on flat nuetral longer and develop their edge angles more progressively using inside foot tipping. Get them to move a bit more forward with the skis as they pass through neutral rather then hucking their CoM to the inside. Get them to angulate sooner to counterbalance their entry and slow down the progress of inclination and hold their hip up and forward more instead of dumping it down and inside/back. Focus on holding the inside foot back. Doing so will also prevent them from dumping their hip down since the foot will be in the way. By this they will tend to only go down as low as they actually need to as the edge angles develop. Teach them to let the turn and angles come to them rather than trying to force it by throwing themselves down into it. Patient development of edge angles. Develop the edge angles from the feet up, not the CoM down. Let the CoM move inside and down as a result of achieving the edge angles, rather than throwing down the CoM to create edge angles.
Someone can still get long leg short leg while dumping their hip but their inside foot will be ahead eventually. Keeping the inside leg out of the way you want to shorten it just enough to keep it out of the way, but hopefully it should not be supporting your weight anyway and that should have little other impact on the edge angle development other then just keeping it out of the way. The edge angle development should come from the CoM moving through due to turn forces and inside foot tipping. Counter balancing with angulation regulates the speed at which your CoM topples inside, and that is what hip dumpers probably need to work on, angulating earlier to slow down that process, and improve their inside foot tipping as the primary mechanism for generating edge angles.