I know uber late. but lol. the p3 is trash, even fully upgrade it gets its teeth kicked in by everyone (yes in 4v4), the bigger threat is the flak+pg combo
I tested this several weeks ago, and fully upgraded p3 wins handily against both the normal sherman and upgraded crusaders. Against hellcat it was a 50/50. If free vet 1 rapid fire was used, it was obviously a stomp.
And anything bigger, p3 lost.
And that is if you would just stand there unmoving, you also have the fastest speed out of all mediums, self repair, emergency smoke and capping ability
This 4v4 experience you are referring to, is it in the room with us right now? There is some stacked (asian) teams roaming around in 4v4 that abuse Wehr Coastal/Mech or DAK to a level you probably can't even imagine