At this point I might just be getting paranoid, however seeing your comment of "If this doesn't bother you, then you ain't a true fan on FT" I simply consider this some kind of an underhanded rant again on one of FT's many supposed 'flaws' by someone who dislikes FT and for some reason can't just ignore the series and its fans and pretends to be one just to rant on it.
What you just described has been present since chapter one. How was it possible that Natsu and Aquarius heavily damaged a port without any people being dead or heavily injured? Realistically there should have been some major casualties there, but there seemingly weren't any and Natsu and Lucy ran of laughing and there are countless of examples like that throughout the series. It simply is like that as if you have to start to become more realistic about the consequences of actions like these, Hiro would completely need to alter the series to something that isn't FT anymore. It is what it is for the simple reason that FT is not a manga that wants to make the concept of 'death' omnipresent. This is also not something FT has a monopoly on as it frequently appears in many other series too.
On top of that there's a difference between a one on one fight between a human and a dragon and groups of humans ganging up on a single dragon. Even if a single human can't kill a dragon, that doesn't mean a group can't do it either.
Secondly as said these dragons were barely serious. They were not mindless puppets of Rogue, Atlas Flame betrayed Rogue and especially Zirconis was just messing around. It became quite clear from several things several dragons said that they do not really consider humans a worthy species. You are talking about a supposed statement Hiro was trying to make according to you, while the entire conclusion that was draw from these fights against the dragons was that the Dragon Slayers were not on a level yet they could beat a dragon. This is completely the opposite of your statement.
Thirdly there were people who died or who were about to die, but got saved by Ur's Time Arc magic. Agreed that wasn't the best scene Hiro created, but it remains so that there were actually people who 'died' at one point.
Lastly there are many series who intentionally kill nameless characters by the dozens, but let all their main characters survive just to show that there is 'realism' in what they write, but honestly I don't find that much better as it's not hard to kill off characters like that as there is no emotional attachment. As FT isn't a series, and shouldn't be one either, that focuses much on realism and death, there isn't any need to do that. Someone who says something like that you are not a real fan if you are not bothered by something like this, might want to rethink his own status in regards to a specific series. You can find it annoying that people don't die left and right, but don't decide for yourself what a real fan should be bothered by and what not.