I've seen absurd scenarios where a 2 vs 4 is won by the 2, but generally, the team with the more people wins.

Let's talk value. You can generate more money by making a single last hit per minute than a leaver gives you passively (25 gold per minute for a single leaver), in fact, a leaver is comparable to the money aura one of the neutral rats has, which is unanimously agreed to be the worst passive skill Doom can copy in the jungle. In fact a teammate can even generate you more gold by being present, all they have to do is stack the jungle once every 3 minutes and done, they're far more valuable than a leaver.

But a leaver means you lost a teammate which means one less source of stuns and whatnot. You have less actionable manpower in return for that marginal amount of money. And that's just not comparable. Even an item-less Sven can stun your enemy core and buy you 3 seconds of free hits on them. You have to pay 6000 gold and use up a slot and lose the timed-opportunity to buy something else for that effect with items.

With more and more leavers, this becomes more complicated. Yes, each of you individually gets more gold. 66 gpm with two leavers. But, if you're at 3 and below players a problem occurs: The map becomes too big and wide for all of you. You don't have enough manpower. You become susceptible to ganks and splitpushes.

Allow me to elaborate: Dota is a game with three primary driving tactics in roughly a rock paper scissors disposition. Splitpushing beats Grouping Up, Grouping Up beats Ganking and Ganking beats Splitpushes. With 3 and less players you largely lose access to anything other than grouping up and pushing. Because if one person is told to defend or farm alone, they get ganked. If you try to push, you get enemies forming distractions elsewhere that you can't respond to without losing firepower.

Let's push as 3. You can still win a 3 vs 5. Enough items and spells to go around and maybe you blow someone up and make it a 3 vs 4. Easy win! Okay, but what about... You can win a 3 vs 4 + a splitpusher. But are you faster at winning a fight AND pushing than someone pushing solo unimpeded tho? And you can win a 3vs3 and push... before losing two towers against individual splitpusher solos either. You're now entering the realm of trading towers at a loss. But worse - the solos can even split a tower AND cut your wave behind you. Basically, they waste your time and take value, and next time, they'll do it better.

So, just tp someone back to deal with it? Or blink backwards? Congrats, now it's a 2vs4, or gasp a 3vs1. Kill them near your base? Your tp is on cooldown and you have to walk back to push with your other allies - oh oops, they'll revive in time to defend. No progress. How do they even know where you've been moving? Oh, right. They have 2 supports that can afford to ward and give vision instead of focusing hard on objectives.

The longer it goes, the worse for you. Take rosh? Lose a tower. Chase with two top into the jungle? Yeah they were in your triangle and top jungle taking turns shoving the other waves and are now at your Tier 3 lowering your future gold. You think you got a kill on two, but they pushed and got tormentor and now venomancer has something that will waste 2 seconds of your BKB that your leavers didn't even fully pay for a third of.

It's actually a good sign that you may believe a leaver impacts the team positively as that might mean the people you're playing with are just... Too bad at dota to strategize like this. But it should not, under any circumstances, be representative of higher tiers of play unless of someone lucks the shit out of what heroes they had. Ember Spirit, Nature's Prophet, Tinker, Old TA aghs, and a couple others can handle player deficits better than most. The 2vs4 won by the two? It was a Nature's Prophet and a Pugna microing the leavers, one of which was a naga who could push with illusions and sing to stall the 4. Luck played a gigantic part in that win.

It's weirdly also good that you see leavers with some frequency too, it means that the game didn't lump you with smurfs. Players leave game less often the more dota they play.

So, depending on your skill bracket (which as you are newer, probably skews lower) this may happen more or less frequently, but I can only speak to when it happens to me.

When somebody abandons a game, it becomes safe to leave. This means, you can go to to the menu, leave the game, and immediately queue into a new game without any penalty. For myself, this is a fine solution because people don't abandon very often, but I can imagine this being a poor solution if abandons happen too frequently and you just want to play the dang game.

I also prefer just leaving a game with an abandon-er because the effect you describe is definitely real. There is an advantage for teams with 4 players, especially earlier in the game. In an ideal world the gold redistribution would be scaled to give both teams equal odds, but even that isn't perfect because your team technically still has the advantage if they can survive.

At some point in the game, the hero disadvantage should(?) outweigh the gold advantage. So, if you're looking for a general strategy for winning a game with a leaver on the opposing side, the goal is survival. You have to play as if the enemy team is way ahead in gold, because, well, they are. It also requires a much heavier emphasis on team play. Any one of their heroes is likely stronger than any one of your heroes, so your team will need to work together. There is also a double-edged sword to having fewer stronger heroes: it is more punishing for them if a teammate dies. So if and when you manage to kill an enemy hero, there may be bigger than normal openings for taking objectives (towers).

Having less players is always worse. In my bracket/region, usually the team that has a leaver simply leaves the game as soon as it's safe to leave, since they're almost guaranteed to lose playing 4v5. Only exception is if the game was already going very long or the leaver team had a clear advantage.

Let's talk about the real impact a leaver has: around 20 minutes, the top cores maybe have 10k networth. For ease of calculation, let's say the leaver has all of that in items. That means when you sell their items, your team gets 5k gold distributed among the remaining players. That's 1250 gold per hero. Sure, those 4 players may now be a bit stronger. But also, the whole team just lost 5k gold instantly, because you only got half the money when selling items. A 5k networth swing at 20 minutes alone is already pretty bad. But you also lost a whole hero. And this also gets worse over time, since the hero doesn't earn any gold except passive gold anymore, which is so small to be negligible (as was already said, it's less than 2 last hits per minute, which is laughable).

So just viewed objectively from the state of the game, having a leaver is terrible. There is no gameplay reason that a team with a leaver should win more often than not, in fact it's such a huge disadvantage that it's pretty normal for the leaver team to just stop playing.

So there are two things to check here: One is, do you really consistently lose against teams with a leaver? How often does that really happen? How many leavers do you get? I have one maaaybe every 20-50 games, so every 15-35 hours, even if I theoretically would lose against leavers more often, there is no way I would notice that because it just happens so rarely. Did you not just maybe randomly lose 2, 3 games in a row against leavers and extrapolate from such a small sample size? That could just be random events because the enemy team already was really far ahead in these games, so while having a leaver is devastating, they were already so far ahead that it didn't matter too much.

The second one is mindset, for example it's not very uncommon as the team without a leaver, to "stop trying" as hard and mess around a bit, because "the win is basically guaranteed"... but if you do that during the late game without a buyback, it's really easy to still lose the game. Even though you have a huge advantage, if you just play proportionally worse, of course you can also still lose.

The only way to really help you though is for you to give us the match IDs in question and let us take a look at the games that you lost with a leaver. Without that, everything is speculation.

IMHO, it’s not that it’s unbalanced, but rather it’s the only way to give an advantage over a disadvantage. You’re literally down a player.

There was intentions to let other players join mid game to fill the slot, but never was implemented.

Until Vale comes with another idea to level the playing field, we are going to keep having levers, but also a chance the team uses the lever in a bad way (buying incorrect items).