My barbarian slam no longer interrupts
 

Sometimes it works - instantly, the spell ends the moment I hit, but now in my 30s it started to have mobs regain concentration and continue casting again.

This even counts for mobs I could interrupt reliably before, such as Pickclaw cabalists, in my 20s.

is this normal behavior?

perhaps post it in the bugs area

I've noticed this as well.

Danth