This is very true - we found this to an extreme degree with one very unusual prototype driver we had made. That speaker used an XBL2 motor, with split gap and short voice coil so it could do massive clean excursion but it didn't have enough voice coil area to get rid of all the heat at high power. During testing we blew three drivers without them even distorting, they sounded really good, went super loud and then started smoking and suddenly cut out. The fourth driver was saved and went off to be a recording studio cab. The 3015LF was a bit like this too, though to a much lesser degree, otherwise they wouldn't be such popular speakers.
The way I see if, when it comes to making a driver robust you need to have a big enough gap between Xmax amd Xlim (aka Xmech) and enough thermal power handling to allow you to exceed Xmax without thermal failure.
Xmax is the point where the driver reaches 10% distortion (due to over-excursion making the magnetic force and/or the suspension non-linear). Xlim is the point where the speaker is damaged - cone creasing, buckled voice coil former, stretched/warped suspension, etc. My pre-Barefaced cabs didn't have enough margin between Xmax and Xlim so the cones got creased when they were pushed too hard.
So we've done our best at Barefaced to make cabs that you can push hard without worrying about blowing them. With the 12XN cabs you can just follow the power ratings - the 12XN very obviously goes from clean to (not very pretty) distortion when you push it too hard. With the 10CR cabs it's a bit harder to tell so here's a deeper explanation:
10CR power handling
