Regardless of OP there are issues with the Su-76.
Some of those are:
Very low XP value.
Combination of barrage and vet 1 ability trucking allows the unit to spot or have mini-map information for more effective barrage.
High far penetration.
The ability to break off barrage instantly
Can crush humans
My suggestions would be that barrage:
Xp value increased to much cost.
Barrage replaces "tracking" as a vet 1 ability.
Barrage now make unit immobile for the duration
Lower far penetration
Remove crush humans
