There are several imbalances and I think that's a better word than "fair." Right now there are a handful of teams that even if you had a Character GP that was 500K better you still couldn't win without having them unlocked, geared, and zeta'd. I can't tell you how many higher GP three-man squads I put up against the unbalanced Nightsisters defense... or what's it like having an opponent with my same GP who somehow has a maxed Treya. It's things like that which throw Grand Arena into crazy space.
They've simply built too many potential squads without decent counter squads. That's all.