Disclaimer: I do not think laser rifles are overpowered, and this thread is not about that.

Right now there really isn't much incentive to use the advanced laser rifle (Elm 7) over the standard laser rifle. It overheats a bit less, but that does not make up for the higher price tag and fitting requirements.
A damage buff would make the Elm worth using over standard; the base damage of the standard LR is 15, and the Viz is 20, so 17.5 would be a good damage for the Elm since its in between.
In exchange, the Elm and the prototype laser rifle could all get the same overheat rate. The prototype laser rifle having its overheat rate increased might please a lot of those screaming for a nerf.

Regarding the skills for the laser rifle, as Aeon Amadi pointed out in his thread that the skills for laser rifles seem to be fighting against each other. Laser Rifle Operation gives a 5% reduction to heat build up per level. Laser Rifle Proficiency gives 5% increased cool down. Please have a look at this thread.