I have recently gone from around +55 win loss to +75 win loss, and I have noticed that my average teammate has gone from around 500-800 wins to somewhere around 200. Along with that, the level of play has decreased sharply. Is matchmaking compensating for my higher ELO and matching me with lower ELO in order to balance out the teams? Has anyone else noticed this as they reached a higher ELO?

Matchmaking can be wonky.
I played with you the other day, and it is entirely possible the issue was the fact that it was during the the Dominate Dominion Tournament #38. Most of the high Elo people I usually play with were in the tournament, and thus matchmaking had to make do with who was online at the time.

I believe Sauron can confirm that matchmaking will place higher elo people (and premades) on the opposing team and lower elo players on your team if you are unbalancingly higher elo that whoever is on at the moment.

that's my 2 cents for you, FFIW