Staghound needs more fixing than T17. The prob is that neither has a real hard counter aside from a p4 or higher. Paks+shreck way underpreform vs these 2. As has been said before, their accuracy on the move, their armor type and their speed need to be tweaked.
By lowering piat pop arent we just begging for more spam? I know they underpreform without vet, but at vet3 they just melt face through builddings. Im not sure whatthe solution is here.
I don't think PIATs are as much of a concern at higher vet because they're easy to dodge due to their low speed. I do, however, agree that the staghound is more of a concern. I hate t17s but I usually blame myself and only myself when my armor and other units are taken down by them. If I'm more aware of their presence, I can nuke em.
The only problem with the piat is IF it hits you, it does uber damage, but you can dodge them if you're careful and they fire slowly. You are right about the spam issue tho. If they're spammed, then slow fire rate won't be as big of an issue.