[c_of_red]

It's called combined arms for a reason. If you have a single unit that is unsupported, then it should be swamped and killed. Your 'soak off' is the game version of the single most common tactic every invented. It's presenting one unit with more targets then it can deal with.
This tactic is several thousnd years old and has survived the transition from clubs and spear thru Swords and Pilum thru Heavy Cavalry right up to Star Wars. The current thinking on defeating an ABM system is giving it more targets then it can deal with, which is the same thing the Roman legions did 2,000 years ago.
No, the tactic of swamping a single unit and overwhelming it with numbers is best countered by not leaving a unit out where it can be swamped. The Mil-speak term is unsupported.
In game terms, you need to have another unit with it's range set to where it will op fire at an enemy that is closing in for the kill. What works even better is having the rest of the platoon supporting.
Gaming the system by giving an unsported unit a majic weapon that can fire hundreds of times faster in the game then in reallife and never runs out of rounds is sort of silly, when it is easier to just learn the proper tactics.