That's why I have not implemented the Refined Elerium Ammunition yet
That ammo is meant to be XCom's response to a new weapon I want to introduce for Aliens to help make Flying Suits less impervious to damage: Anti-matter plasma. It will also be HE ammo for regular alien guns (but unuseable by XCom). Reaching that point in the itemLevels represents the aliens giving up on infiltrating/converting Earth and deciding the terrorize it into submission/annihilate the population. That tech is also unstable by design, preventing the humans from reverse engineering it.
There is also no need to go crazy with the numbers. Explosions target underarmor on direct hits, unlike AP, so even lower damage could be more damaging to aliens. It has the bonus of not going through AP resistance against mutons (although some other aliens also have HE resistance). A narrow miss still does damage if you can catch the alien in the blast. And you can also limit the blast radius (1 for pisols and rifles, 2 for heavy gauss I was thinking).
As for gauss autoshots, I find the lack of it to be a great distinguishing feature in the XAE where Gauss is more accurate, slower and has no autoshots, making it great for longer range engagements and support/sniper operatives, but lasers tend to be better at short range due to rate of fire so great for breachers and scouts.
Maybe a 2 shots autoshots for the 2nd tier gauss rifles could work to make it more attractive to the line soldiers. Currently I keep the same rifle and add new ammo, an advantage of Gauss compared to the ammoless lasers for which you need to make new rifles to get better.