343 Industries, the multiplayer-gameplay has definitely changed.
I particularly like / play the 3 v 3 Heroic A.I. mode.
The changes I've noticed in that mode is that the early, massive rush assaults by the enemy A.I. have been tuned down a bit or are less frequent in said matches. Based on my observations, enemy UNSC A.I. tend to do the early assaults with Vultures, Hornets, Warthogs, Jackrabbits, or Scorpions. Before, it was was with Hellbringers & Cyclopses. Enemy Banished A.I. tend to do the early assaults with Banshees, Jump Pack Brutes, Goliaths, & Brute Choppers.
The gameplay can sometimes be, for lack of a better term, "predictable". Another thing I've seen is that enemy A.I. typically do an early assault against one player in a 1v3 fight while the other 2 players are building their armies.
It also seems like the Banished units are a bit weaker than the UNSC units, on Defense and Offense.
Currently, it seems like Kinsano's leader powers, Inferno and Napalm Missiles, are a bit too lethal in their strength.
Isabel seems to have the least useful or appealing leader abilities. Recently, it seems like the Mac Blast strength has been increased to compensate.
Overall, the gameplay does make players adapt their tactics to counter or reach a temporary stalemate with the enemy A.I. Whoever responds faster will win the match.