you are taking a loss in 90% of cases. the other 10% is going to be all on your team mates, with you pretty much being nothing.
the ban thing? you won't take a ban unless you do that a great deal of times. considering that I'm saying, "if your comp fucks up just don't connect" it shouldn't happen too often, so no ban.
The real selfish thing to do is stay.
Think about it. it's a 4v5 in that game. you come back after first wave and your opponent will easy kill you with their level advantage, if you play safe and avoid that fate you are still the easiest jungle food, and will be a target for ganks and roams.
Plus the fact that while behind you lose the ability to scale, you won't do damage, and you can't afford to build tanky either, as by the time you finish any armor it's going to be too weak to defend you from anything.
If you were a gold starved class like jungle or support just expect to not finish an item before laning ends.
and then you have done more than just dc, you have fed. you couldn't have helped it of course, but you have done it. now your team needs to deal with having a teammate down while a handful of enemies are stronger than hell. this is assuming the advantage on the enemy team has not spread.
and that is the game you chose to be part of, you could've stopped it and prevented 4 others from having a shitty experience because of you. but you chose to stick it out so that you wouldn't risk a ban.