:
= Breaking the meta or trolling. I've heard both.
I play her as a tanky initiator/fighter on occasion. BoRK is another offensive option as well as opting for IBG over Triforce, the rest of the build is centered around tank stats in the form of Randuin's, Warmog's, GA, and Thornmail, building against the team you are facing. It looks a lot like the AD Fizz builds you see.
Basically, it boils down to if you are successful or not. When I carry a game with this build, people go "That ADC Diana carry" and "Holy crap, that kinda works". If I'm unsuccessful and do poorly, I hear "Troll Diana build, WTF" and "Report Diana".
As an aside. I don't play Ranked, which may be what the OP is upset about; when someone plays something that could be considered trolling in a Ranked game, but I would keep an open mind if I were you. Sometimes the people who are using this "Troll pick" are actually pretty good at it because they have practiced it quite a bit. The first time I saw AD Fizz, I thought my teammate was trolling. The same when AD Nidalee was a thing, but these things were actually meta once. In addition, did you know AP Gragas was the meta all the way up to when he was picked up with Cinderhulk in the Jungle :O? I was actually harassed by teammates when I played Gragas with this build:
in toplane "WTF, you do no damage, you need more AP". Months later, Gragas' tank build defined the meta. I'm not saying that AD bruiser Diana is comparable to the thought process behind AD Fizz (which was pretty ingenious) and she doesn't have AD ratios like Nidalee, but she does do very well with Spellblade effects and Attack Speed and she is a great duelist (bonus points for throwing off your opponents itemization).
Anyway, that's my piece. There is a lot to be said about when your teammate is trolling or they are actually pulling off something viable. If they are legitimately trying, though, and you can see some reasoning behind what they are doing, I hope you keep an open mind, because it may surprise you.