MOBA s wouldn't be so bad if they didn't suffer from run-away snowball effect
MOBAs actually have built in anti-snowball mechanics, inexperienced players usually just don't realize it. For example, if somebody goes on a killstreak (say 10 kills in a row), the first person to kill him gets 1000 gold. Also, if a team is doing better than you are, it also means they are probably significantly higher in level. Since experience and gold gained is based on hero level (of the person you've killed), in practice this means that you get more than they do for a successful kill. For the most part, the more ahead you are these games, the more you have to lose. However, even with all those mechanics, it is still very easy for the game to snowball if there is a significant disparity between the skill levels of the two teams, or if one team has much better hero lineup than the other; but the proclivity for the game to snowball is much better than say, Starcraft 2, which has no mechanics to help the player or team that is losing.
and if killing blows were not all important, But I am pretty sure that would make them no longer MOBA s
The killing blow point I completely agree with. It's extremely counter-intuitive, especially to new players, to be giving up killing blows on purpose. Often it results in the hero escaping, and the person who was just trying to be generous gets blamed for it. However, when said person takes the kill to make sure the enemy doesn't get away, they also get blamed. It's often a lose-lose situation.
A week ago I would have agreed with you, that without the killing blow mechanic, MOBAs wouldn't be MOBAs, but I recently read a blog post from one of the HoN developers that changed my mind. If you are interested in MOBAs at all, or would like to see interesting ideas on how they could be improved, I would highly recommend the read. http://s2nome.wordpress.com/2011/06/07/denying/
Without a leader, the best thing you can do is to politely suggest, but this can be difficult in an environment where you are stuck for at least 20 min. with players who might be terrible and hostile. The penalty? You don't get as much IP, and you could be wasting your time. Even worse, some players that AFK at the fountain get all of the IP and do none of the work. This creates even more animosity that carries over from game to game and helps make league of legends the paragon of humanity that it is.
AFKing in the fountain is more of a League problem than HoN (and I'll assume DotA 2) because doing it in HoN will ban you from matchmaking, and not temporarily mind you, until you can prove that you deserve to play again. Having to pay $30 for the game allows the company a greater influence over what each player does. However, this creates another problem, as I said before, of forcing angry players into a situation that they would rather leave.
I grew up in a time before the Internet, and I was taught phone manners. The younger folks today do not seem to have that hands-on parenting. I often see an egocentric mentality where the player feels as if they are the only one that matters, to hell with everyone else; if they die in league of legends, it's someone else's fault. Nobody takes responsibility. It's going to be a very long life if you just blame everyone else for your life instead of doing what you can to influence the outcome.
I've seen this pattern too, and I find it to be a larger problem with society, not just individual people, or the demographic of gamers. I'm 24 now, and growing up with my generation has been a nightmare. They do seem very egocentric, most of their parents never taught them respect (including mine), and they always want to shift the blame onto somebody else. Judging from what I've seen, the generation after mine is only going to be worse. It could just be the U.S. though, I've heard that in some other countries around the world, respecting your elders is still extremely important, and I've seriously thought about moving to one of those countries more than once. Obviously, this failure of parenting/education has a much more far-reaching effect than just gaming, but since gaming (MOBA gaming in particular) tends to bring out the worst in people, it makes encountering it commonplace. And yes, this "it's never my fault" attitude, does tend to make everybody miserable, in and outside of the gaming world.
Lastly, what about those people that say "you didn't call MIA!" Who invented this? If it's so critical, why isn't it coded into the gameplay? When I play the game, I have one eye on the map at all times. All you have to do is count to five. I expect other players to take responsibility for paying attention because we are not on voice chat. If I say MIA, it's more of a courtesy than anything. If you are positioned properly, it won't even affect how you play. Other triggers include watching who just died. It's also not terribly difficult to do proper positioning, and there are secondary skills that will help you dodge and weave. Take responsibility for when you die, it goes a long way towards a happy team and will help you in real life.
MIA (missing in action) was originally invented for DotA, and is a short way of telling people that an enemy has left your lane (and is therefore, unaccounted for). One usually says "bot mia" or "mid mia", depending on which lane they are calling. The problem is yes, the player has to stop what you are doing to type it, which can often get you killed, or at the very least make you waste precious time. Your personal ability to watch the minimap and count enemy heroes while still playing the game is impressive, but you shouldn't assume that everybody has the talent to do that as well. I've been playing these games for 7+ years now, and I still can't do that.
In terms of why there isn't an in-game method for calling missing, your guess is as good as mine. In DotA there wasn't one because it was simply a Warcraft mod, the engine not being designed for the map. In HoN you have voice chat, where with the click of a button you can tell your team not only that there is someone missing, but who it is, and where you think they're going, without interrupting what you're doing (there are also user-created mods that put buttons on the screen which you can click to do it for you as well). In LoL...I honestly have no idea.
edit: Maybe we should move this to off-topic. Sorry