Most players (most!)... when they join a new team... they have to feel-out what role they need to play.
Hitters, often, take themselves out of a play - which some coaching staffs & systems very much dislike.
If a player is going to throw a hit, it is usually part of a system where all on-ice teammates know that they need to cover for that player.
CAR was a very solid supporting defensive system... so one player could throw a big hit and the others would be able to cover marks for that player.
I think Faulk is playing a bit "safe" until he knows when/where he can make the risks to play a little more physical.
The Blues defenders have never been a bit hitting (by quantity) group. The forwards do the hitting on that team.
I think you give Faulk another 2-3 weeks... that should be enough to see if he'll ramp back up... of if this is his new role.
HITTING is VERY overrated (IMO) for defensemen... Nick Lidstrom was never a big-quantity hitter and he was just fine in a defensive role.
This is a concept that people in the analytics/management roles are very aware of these days in the NHL.
I think we'll continue to see Hit-quantities for Defensemen drop... along with D-size... in favour of D-speed and footwork.
This decrease will actually put a PREMIUM on the HIT/BLK NHL-defensemen that do still exist.
Food for thought.