I've been a pretty outspoken opponent of the new Matchmaking, and GAC in general since the beginning. Matchmaking is completely arbitrary and the results have no bearing on who would win an actual head-to-head match up based on the "rankings". I could easily beat accounts that are ranked ahead of me and who have gotten there by virtue of matchmaking, just as there are players below me that could curb stomp my roster.
That said, matches are much closer than they were in GA. This isn't good for me personally, as I'm on the low side of the GP range for D4 and am always at least one squad undermanned against players that already have enough GP to be in D3. This extra squad is invariably Geos, Shaak Ti / Clones, or Padme and I actually lost twice in a single week, both to players that have maxed out GP for the division and had a team I haven't had a chance to build a counter for yet. Compare that to the single match I lost in the entirety of GA and you can see why some of us have big questions around WHY matchmaking is this way.
Limiting matchmaking to within the Division was a positive step forward and has stopped the worst of the mismatches (getting matched up with accounts with almost 700k more total GP and more squad selection / available counters). As much as I wish GAC were a different thing, I think a few more tweaks, most noticeably around the outsized GP of Zeta abilities and lack of G13 GP contribution, and matchmaking is in as good a state as it can be in.
I still disagree with the "everyone gets an equal chance at a trophy" mentality that is this GAC format and driven by this matchmaking, but if that's the design intent, matchmaking is getting close to making that happen.