I second the group firing, especially on a mech with multiples of the same type of weapon. If you group by arm location, you can even use the group fire to only fire the weapons with an open path the the target if you are peeking around a building, or if up close and you need to adjust right or left a little. This also allows you to regulate heat very efficiently.
I even to group my left arm on the left button and right arm on the right button and secondary weapons on the mousewheel when there are mixed but similar weapon types so firing kinda feels like a one two punch style, give em the right, then follow with a left to finish off if needed.