99.9% B.S.
We have yet to hear of an invisible plane that someone could actually prove killed someone. The few people that have discussed this on open buffer (flying as an invisible plane) stated that all other planes appear as distant dots only. All the other rubbish is poor SA or connection related. I kill people daily that never see what hits 'em, and I don't have to be invisible to do it. It happens and I have film to prove it.
As to invisible Panzer rounds, it sounds like you would not have lasted long anyway. 800 feet? Even at 800yds. you would not have time to translate your turret. I had three panzers bullseyed at the spawn point off of 69 just yesterday. I could see them in total confusion, hunting the hills for my location. I gave them no mercy as I called for supplies. I used no tracers (to hide my location) and at 2.6k kept them wrapped up for quite awhile.
It sounds to me like you received a brutal beating. Running into one of the games' veterans can be quite frustrating. Perhaps, if you had chosen more carefully you would have come up with a more successful experience. To me this game is the best thing going.
If you decide to return, I will be more than willing to show you a few trade secrets, though I am by no means the best in the game (in any category). I am sure I am not alone. This community does what it can to support people willing to try. Further, there are many individuals about that come up with thoughful, productive input about gameplay issues; AND HTC listens to their customers. I have been a subscriber to many other services that failed in that regard.
Regards.