With the introduction of the PA-30, you've now included CAR 3 into the certification mix, per the Type Certificate Data Sheet.
I've spent a considerably amount of time flying light twins from rough fields, dirt airstrips, one-way box canyons and the like, and have some appreciation for the requirements to operate them safely.
An airplane such as the PA-30 isn't really a single with two half engines when it comes to losing an engine. Nearly 80% of the available effective thrust is gone when dealing with the assymetric thrust condition. Whereas climb performance is determined by excess thrust, there may very well be little enough to leave no climb at all. What there is, however, determines how fast you drift back down, and subsequently, the point on the earth to which you drift. A very big consideration in getting back down.
We had a PA-30 for a time. I didn't much care for it, but it did the job. Much of my career in flight has been spent at very low altitudes, and that included much of my early twin flying. Climbing to a "safe" altitude was never an issue because we'd never be climbing there...even when I got to four engine airplanes, we seldom climbed above 500', operationally. Accordingly, not having the luxury of time and altitude, things had to be done right...which always included for having the necessary performance, planning our relationship to terrain well in advance, and always leaving an "out."
I submit that this is good practice no matter where, or what you fly; it worked for me then, it worked for me now. Trying two eek out of the shortest field you can, below Vmc, may be something you get away with for a time. It's not something you'll get away with for all time, nor is it prudent.
The specific certification numbers, as previously discussed, do not necessarily equate to the real world numbers, but one must remember that while the published minimum control speeds may be decreased by density altitude (normally aspirated light twin), reduced thrust takeoffs, different weights and forward CG's, the real world counterpart to those numbers may also be higher than published due to crosswinds, runway condition, cold temperatures, pilot reaction, a tired, well-loved airplane, etc.
Being conservative is a professional act that serves the interest of the airplane, the passengers or cargo, and certainly the crew.