After 12 hours of PP, I decided to restart. I find that the default Veteran difficulty is just too easy. My team of 5 can take out any threats and I became bored actually. There was nothing threatening about each mission anymore. I restarted the game as Hero and, aha, I must say this is more like it. I need to use strategy to survive. In every level, the Pandorians will start to swarm you and so, early in the level, I retreated my team into a room, higher ground, and wait for them to come. After just two hours, I know I need to build a B-team, which I never did under Veteran difficulty.
On falling back and defending from inside a room, PP does not seem to encourage exploration. I used to break my team into two, combing two sides of the map. Hero difficulty though, will mean that one team usually get wiped. So, it’s best to stick together and defend and wait for them to attack. This seems to work, but the downside is that there is no exploration.
I can’t make up my mind what I like more :)