I heard that playing as a support is a good way to raise Elo rating and get out of 'Elo hell'. What advantages does it offer over other roles in this case?
To be honest, it really isn't. With the meta that is going on right now the support does not get as much money as the rest of the team, and usually does not do as much damage. Mid or Top lane are usually better at carrying a game because with a solo lane you get more experience and it is much easier to get kills when there is only one enemy in your lane.
I personally would suggest playing as a supporter to boost your ranking. The reasons are simple: - There's only a few people who really want to play the supporter -> if you pick him, there's not gonna be fights about who plays what. -> better mood -> better communication -> no ragequitters - If you're good you can let your ADC get fed... and if he carries the game, gg easy. - Many supporters are too stupid to ward the whole map. So instead of QQing cause of the lame supporter you take the role yourself. Make sure to buy that blue Sightstone and ward everything that is important. -> more chances to win. Wards let you win games. - If you have a good CC and you're good engaging it depends on you wether you win the teamfights or not. If you feel like you're good doing this it will automatically let all of your teammates get more kills, gg easy. - I think that's basically the most important things that secure a win. Gl hf.
I don't know if I'd say support was the easiest way to gain elo, but a support who is doing it willingly will do better than someone forced to do it, and the difference between a good support and a poor one is huge, especially if you're actively zoning the enemy from gold/exp, while the other support is just hiding in a bush healing whenever. Supports also have a tendency to be the objective callers, since they probably have the most map awareness on the team (where the other team is, how weak/strong they are compared to yours etc)
If you are a good support you can feed kills to your ad carry, even if they aren't that good a feed ad carry is a feed ad carry. That in turn makes the other ad carry that much weaker the more you kill them and deny them farm. A good support with anti iniate skills like janna, lulu, or sona can pretty much win an entire team fight depending on when and where you use that ultimate.
Depending on your bracket, support is absolutely a viable way to raise your rank.
Some quick and easy steps that can set the support apart from the enemy support:
1) The number one deficiency in low elo play (1200 or so) is easily ward coverage. Look at any pro's solo queue stream, then look at a low elo solo queue match. World of difference. As support, keep your lane warded during the laning phase. Consider making a quick trip mid on each back and ward either the enemy's bush (on wolves/blue side) or up near wraiths, whichever's closer. Continue your warding into the late game.
2) Keep timers on your and the enemy's buffs, and send out reminders in chat a minute or so before they spawn. This is so rarely done in lower elos, but challenging buffs is extremely strong (and if you catch your opponent off-guard, can lead to some kills). Measured aggression is the name of the game.
3) Keep an eye on your mini-map. If an enemy crosses a ward, immediately fallback-ping them. Map awareness is another thing that separates low elo from high elo. Since you're somewhat less active as support, that gives you plenty of time to make up the difference for your team.
These three steps are easy, take no skill and not much effort, and can make a world of difference.