If you want to PK, then play on a PVP server.
Additionally, I'd say that if you happen to (with all your shit on) agro a fel cannon and it happens to hit people around you, then no...Blizzard isn't going to care. If someone is running around naked using the environment to PK people intentionally...pretty sure they'll take action (eventually). Especially since in their TOS there's a blind paragraph about how you cannot make people feel bad, or harass them. They obviously don't usually enforce the whole 'upset others' thing, but it's there for leeway on shit like this.
As far as GMs saying they don't care...there are some moron GMs out there. We had people exploiting the box in Area 52 (they could stand on it, and PK without guard agro), and had to go through 3 GMs and a phone call to get shit done. The first 2 GMs only saw 'wah wah PKing' and as it's a pvp server said 'resolve it yourself'. The last GM finally understood 'exploiting', and that and a phone call had it stopped, and now it no longer works.
They're probably not going to do shit about anyone getting accidentally killed, it's probably intentional. They should do something about people who are intentionally killing others and it's easy to ascertain which is which; if they're doing it repeatedly and if they're naked. Just continue to petition and if it affects you that much, call Blizzard. Also realize that 'taking action' usually means a stern talking to little Timmy, or if he's been an exceptional asshat with many warnings, maaaaybe a 3 day time out.
Though posting about it is a good way to get it resolved too, either someone sees it who realizes it's an issue...or more morons abuse it, which then makes it a big issue.