Just give defenders a way to look like they did more than sit around at spawn, I say.

I thoroughly disagree, if defending gave more points you would run into even MORE situations of 4-5 defending vs 3 enemies who have a nice long-range harass and the other 2 enemies freely capping the rest of the scar.

Defending when you have 3 and enemy has 2, is ok, but when you have 1-2 and enemy got the rest it is ALL about capping faster

Why do you care what you score is?

In a game like CoD or Halo K/D is more important so you can see who is pulling their weight - or vice versa, see who isn't capping points but only going for kills. In League of Legends who cares how many point you have? Especially when the number doesn't effect the outcome of the game.

The score system doesn't change what actually works to win the game.
It only incite players to play badly for the sake of boosting their personal score.

Seems fine to me.

Standing at a tower as a means of defending it is bad strategy.

I have no trouble gaining points while defending, but I don't just spend the entire game sitting at one node.

To me the idea that this is a "non-issue", that score doesn't matter and we can/should just ignore it is silly. If it's going to be there, people are going to pay attention to it.

I tend to play all out tank in Dominion. Leona with all tank items except maybe a sheen->triforce, I can hold a point 2v1 and sometimes 3v1. But otherwise I'm just standing there waiting for them to attack because I leverage the tower to do damage while I'm basically invincible. I'll even clear a minion wave and promote so that they have to pay attention to me or lose a point with no effort. This frees up the rest of my team to maintain the other two points while resources are wasted attacking me.

When I do play this way I'm usually 4th or 5th and we win. If the game is going bad and thus requiring me to attack or I got focused by 4, I go on the offensive and then end in the top 3 (usually 1st), but then we lose because no one was holding points.

So I get rewarded for losing and punished for winning :-/

So, removing KDA from the game was not an option, we got extremely negative reactions from many existing players when we tested that. In fact for a long time we didn't have KDA in the scoreboard in addition to the top right display, but ultimately added it back in based on feedback.

We opted to replace it with a point system for dominion in many areas as a better (but not perfect) reinforcement of gameplay. From that perspective I think it is very successful, I see very few people asking for KDA display outside the scoreboard and the points reinforce more positive gameplay (IMHO) than simple KDA. I think it is an improvement over what we had before.

You know what can easly solve that? Achievements

Things like "most magic damage dealt", "most physical damage dealt", "most physical damage absorbed", "most magical damage absorbed", "most healing done on an ally", "most times CCed an enemy", "most wards used" and so forth

True, we do have (most) of these statistics in our match history, but it could be fun to actually win something based on certain milestones (even if they don't appear during the game, only after the match). Specially if it's ranked on bronze, silver, gold, platinun etc...

Who knows? Maybe then people will actually want to tank, support and do other valuable stuff during the game besides trying to kill everyone (and dying in the process)