November 2018
From what we know of GW according to devs:
Uses the old stat power instead of galactic power.
Does not take abilities into account(for you or the opponent).
Does not take synergy into account.
Based off the top 5 of your roster, not any particular squad or anything.
From what we know of GW according to dozens of campaigns worth of research done regarding what power level was at what battle:
Battle 1 is roughly 60%
Battle 3 is roughly 70%
Battle 9 is roughly 100%
Battle 12 is roughly 115%
Yet people are getting 150% of their top 5 GP as early as battle 1. What unit of measure could the game be using where a team with 50K GP be 60% of another team's 34K GP?? It makes no sense.
And the phenomenon just started in early October. If you look at GW complaints before then it is basically synergy, zetas, NS cheese, and KRU. After the issue started it's teams being extremely OP from a power perspective.
November 2018
I've had this happen again to me today.
Stage 9 of GW and I've been given an opponent that's over 30k gp stronger than my strongest team - 2-3 gear levels higher. I sent in a couple of reserve squads to soak up some of the specials, etc. but they pretty much got wiped before being able to take a turn. My strongest team lasted a little longer but was quickly beaten.
November 2018 - last edited November 2018
I can confirm I witnessed a GW matchmaking lvl 42 player, g5 Phoenix on overall 3 stars (my son) vs level 75, overall g7+, overall 7 stars phoenix squad. Early node, around 4-5.
Tthis was one and one only case I'm aware of. However, the presence of it is a solid proof there are GW matchmaking issues (edgecase).
To avoid speculations - I've checked the top 50 of his arena, around level 50-, 5-6 stars toons, g6, top 3 mixed with g7.
December 2018