The reason the first games are played at such high stakes ELO-wise is that the ELO-system will sooner or later get players into the ratings they should be playing at. Sure, you can lose your first 8 games and drop down to 800 rating (not unlike me in season one), but as long as you keep playing you'll eventually, sooner or later, reach the rating you're supposed to be at.
If a player who should be ranked ~1100 wins his first 10 games and rockets up to >1500, ELO decay effectively prevents him from turtling and keeping the rating without playing, hence again, sooner or later he'll drop to where he should be.
And no, this has nothing to do with the ELO hell we all know of. First of all, it doesn't even exist for everyone, just the 'above average' players (~1500).
A player with a true ELO of 1500 could probably not carry his team at 1200. A player with a true ELO of 2000 playing at 1200 certainly could carry his whole team occasionally, assuming there would be no leavers. He could be carrying all the way past 1700, up until about 1800 rating when he would be ~200 rating away from his true ELO, at which point the win/loss ratio drops to about 70% and keeps dropping further. Then at some point the w/l is 50%, and he's at his true ELO.
Now this true 1500 player could possibly carry his team at about 700 rating assuming he drops that low for any reason, but at 1200 he's too close to his true rating that this is no longer possible. Since people start at 1200, there can be people of all brackets playing with and against you, but as long as everyone just keeps playing they'll fall into their true brackets sooner or later.
This 'WoW-style-ELO' wasn't really realistic and fair. When I used to play (I stopped playing seriously a week into WoTLK), you got 2 rating for a win and lost over 25 for every loss. This was because the vast majority of players were stuck at ratings far below, and if they managed to win a high rated team they would get higher rewards obviously. This happened because the people you should be playing against were slooowly climbing up the ratings, now playing at 500 ELO below you because you started a week before they did. This, in turn, was because they didn't use the placement games. Players who were terrible at arena would start at 1500, and after losing their ten games would drop to about 1350-1400, which meant they would reasonably often be queued against people rated >2000 or even >2200 at slow hours. Needless to say, if you lost to those bad players, for any reason, you shouldn't have lost over ten games' worth of ELO.
tl;dr: if you play lots of ranked games, your rating will match your skill. Period. If your rating sucks, so do you.
Inb4 >9000 downvotes from bad players thinking they're good.