After playing some more: it is well worth the price.
Chosen give amazing dynamic to the core game and are fun to fight against even thou at times it may seem like you try to demolish a wall by face planting into it (ie. if you prefer to build your teams around one-trick pony spec and chosen spawns with close to 100% immunity to it).
They practically destroy the previous source of income and progress. After 2 reports I have below 30 supply drops - not even worth bothering to fly pick it up, due to the activity of chosen, even thou I had all my missions ranked excellent or flawless. At the same time, twice when I tried to establish 'first' contact with resistance in region that should push story forward they sabotaged it changing scaning from <1 day up back to 10 days

). It's a lot more like darkest dungeon now on campaign level.
However there is plenty room to hold back avatar using misssions. And there is a ton of variation to them. Practically everything now dlc related is part of missions, which can dynamically go into missions related to their outcome, research and incorporated to main story line(so DLCs content no longer feels slapped on).
Overall I wouldn't say it's harder (although second retaliation with 3 berserkers, few mutons, various advent and droids plus, faceless did cought me off guard) but it is a lot more... diverese and fun to play - it isn't monotonous as previously campaigns tend to be when you stabilized avatar and just started to grind out the aliens and churning out several squads of alpha soldiers.