Balance is one thing, but another is the rationalization - why doesn't it work on people? It was never explained.
The destruction of the hull can occur not only through direct exposure to high energies. Here is the standard definition
STR_ALIEN_ALLOYS_UFOPEDIA: "Alien craft are constructed from special alloys with unique properties. They are extremely light and durable, and can be molded by electro-magnetic methods. This material can be reproduced and used in many kinds of manufacturing processes."
The device can be an emitter of the electromagnetic field, tuned to change the shape - the destruction of the alien alloy. On living beings, it will almost not work. At least, it is insignificant.
Although, only not in the case when inside the opponent there are implants from the same alloy. But the aliens use them extensively.
There are probably two explanations. Alternatively, another alloy, biologically more compatible, is used in the implants. Either an exposure of the alloy requires a close contact between the emitter and the alloy, approximately the same as for the shocker, contact of the electrodes with the target is necessary.
Addition.I read it and realized that it was not very clear.
I meant that the knowledge of the technology of formation of extraneous alloy and further study of its properties allows us to open its weak place - the ability to influence it with the help of powerful electromagnetic fields, which leads to the reverse process - destruction, instead of formation.
But the use of this process is very limited. The field at great distances is very weak - close contact is necessary, and the exposure time before the destruction begins, is too great. Therefore, in an air battle, it is almost impossible to use a destroyer (even if delivered to the site by a rocket, it will only do a small hole in the hull, without destroying anything).
For a manual emitter I would recommend a long exposure time (not less than 90% of one stroke). And also the need for ammunition - disposable energy sources, manufactured from Elerium-115. This will limit the use of a tool that is too convenient.
Sorry for my not enough english english.
