Well, maybe a lot of people may have posted about this - which I haven't come across yet.
I don't really know for sure how it is being done but I will just post what I can think of.
How is it matched, really?
IMO, for eg, 15k health champs x 10 = 150000 health /rated account.
30k health champs x 5 = 150000 rated account.
So they are considered a match?
IMO, its just so wrong.
I'm coming up with 40k opponents often and then they are fighting my 30k defenders almost everytime. Especially when they banned my very top champs.
Someone pls explain to me how is it fair?

I don't think I am a top tier player but not that rubbish either. But these matchups make me lose until I get so numb and tired of battle ground.