Hell no...
Pocari warned me the SC2 ladder system matchmaker doesn't come remotely close to that...
I think it somewhat balances the mix on both sides, but it's quite possible you end up with someone 4-5 divisions below you on your team.
And that's another reason you really need to look up people in the precious little time you have on choice screen. If you speak up and ask someone about their better role when they haven't spoken up, they usually respond with wanting to do their better role and play better as a result. You really don't want someone who can't do the remaining role to be stuck in it and fail hard due to pick order. Some people will beat their drum about 'SUMMONERS CODE = PICK ORDER!', but if you do try to be polite during choice, more often than not people will try to resolve things into a more favourable lineup.
My other advice is if you hit a super troll lineup and it's certain to lose - take the one dodge if no one else will. You will only lose about 3 points for first dodge of the day and it's worth using when people act like pricks, pick a triple AD carry/triple support/triple squishy jungle lineup that you know is going to lose you 15-22 points. But after that, the penalty goes to 10+ so only use the first penalty dodge. Trust me, taking a 3 point hit and getting to queue up 5 minutes later is better than losing a big chunk of points.
New Jayce and Blitzcrank skins