SU76 is trash

Decided to mess around and try a SU76 spam build with Def tactics. I was expecting to lose but try it out to see if I could make it work.

I was pretty much dictating the game with my normal build, made T70 lost it killing his Flak Trak but was pretty much in control. Made a couple SU76 found his Flak HQ, decided screw it lets try barrage, barely did any damage. Made a 120 mortar which did slightly better until delayed fuse where it did a lot better. Lost both of them trying to take down the Flak HQ, again wasn't really trying to win just doing some test against live player.
Ended up making 3 to try and kill his Sturmtiger and I noticed they take a bit to shoot even though they have high rate of fire. Did some damage but lost them. Expected since they are trash but I didn't realize until the end how bad they were. I rushed him with last bit of SU76 and what I noticed is that if a vehicle leaves the LOS even if it was just hit it almost immediately drops to FOW.

Thoughts:
Supposedly the point of this unit is to work as a crutch if you are behind on gas. Well that can't be since it will only Pen a P4 or lower so it is useless vs OKW which have higher armor units to begin with.
Since it is a LV, if the unit is gonna have horrible stats it should by default come with vehicle tracking when it lands a hit. It is to clumsy to use otherwise.
What is barrage good for? Can't reliably hit infantry or building so what is it supposed to do other than waste muni.
Mobile reserves wasn't to bad, let my Penals vet faster to bully volks around. Would be nice if Teching it reduced cost of T4, otherwise no one is going to do it.