With a few Priests (3+), they will bless it to death... but yeah I don't know about the Ml20.
Btw does anyone know how much damage the Priest does compared to the SOV/OsT arty? I find it more effective since you can stack them because of decrewing to by pass pop cap.
A good hit by the ML-20 will knock off maybe half of the health of a panther, I like artying repairing German tanks as they don't take kindly to having repair crews and pioneers etc blown up by the falling shells.
I like to use the ML-20 in conjunction with a katyusha. (I play 4v4s mostly these days, the rest of the game is too depressing) Katy for short range blob control and the ML-20 for artying Sim cities, expected routes where the enemy will advance and tanks (because the Katyusha can't do a thing versus tanks...) ML-20 isn't particularly good at shooting at moving targets, but it prevents them bunkering down on targets.
I haven't seen the leFH for an age (nor have I used it). It used to be a year ago that I'd be getting very concerned if there was an leFH on the map, the amount of shells it threw out and the non-existant cooldown made it very dangerous to my units. These days if I see falling arty shells, I just shrug, it doesn't do enough for me to worry about. Even the Panzerwerfer doesn't seem like it does much damage these days (speaking from the receiving end here...)