well, certainly, lowering the single-target damage would be a straight-up nerf in this very scenario, but exactly how much lower would ofc be up to debate. to be clear, i'm not advocating a nerf to 1/4 of its current live value but rather sth in the range of 66 to 75%. most of the ram/offmap combos were adjusted in a rather sensible way as well and AT-OW should be no exception. however, by giving it back a bit more multi-target dps through some form of scaling (and maybe some other adjustments like slightly greater targeting circle) it should perform much better versus groups of tanks while still having enough oomph to aid in taking out the big cats. and the emphasis is on aid, since outplaying your opponent should require more than just two button presses in my opinion.
I would rather have it be more effective vs slow and big targets, then otherwise. If you make it more efficient vs multiple targets, the dps will drop a lot.
Just think about it, for ability to work, you need vehicle to slow, otherwise it is a very expensive armor detergent. Unlike AT loiters, you need time to rev up the shell count and if vehicle is fast enough to get out you are getting best case like 200 damage, while best case with AT loiter can deal up to ~500, even if vehicle is not snared.
So the alternative route is having some sort of accuracy dependency that would make ability miss more vs medium armor + reducing the shell count in first 15 seconds of the ability and moving them towards the 25-40s.
Things like this should be approached very carefully, because 4v4 winrates are pretty bad currently, which to
my surprise was fine in 2019 . I still think 4v4 is a stupid mode to play ladder solo, but locking in as allies there and knowing that if enemy is good enough and picks X unit/doctrine, your chances or winning drops substantially, is quite brutal.