I have loved every single moment in Factions up until the nightmare that is Vizunah Square. Two co-op teams might seem great, and if it worked properly it would be tons of fun, but here is what really happens when you try this:
1st attempt - you try and figure out what is going on and fail because you are kind of lost with the whole concept.
2nd Attempt - Another failure when you hit the second wave and get overwhelmed, again not knowing what to expect. So next time you plan on being ready.
3rd attempt through 10th attempt - You fail every time, not because you aren't prepared, because the other team isn't prepared at all.
11th attempt - You fail to the shouts of "haha have fun losers" then the other team quits so you die.
12th attempt - Someone joins the mission on the other side just to cap a skill then leaves, you fail.
13th attempt - Menhlo glitches and gets killed, you fail.
14th attempt - Togo glitches and gets killed, you fail.
15th attempt - Henchies glitch when the other team approaches, Togo dies, you fail.
16th through 20th attempt - back to failing because of the other team not being prepared.
21st attempt - Finally get a good second group and beat the mission
So, tonight after 21 attempts, my boyfriend and I finally beat Vizunah square. Only twice did we ever die/fail to protect master Togo. In every single other case it was the other side that somehow caused us all to die and fail the mission.
I think this is a really neat idea in concept, but the reality is it can potentially take dozens of tries to finally finish the mission because of getting paired with a horrible team or some npc bug causing Togo or Menhlo to get stuck
When it finally worked as intended, it was a lot of fun actually. The problem is there is too much room for it to not go right at all.