you'll see when it raises its hands up high, if you see him do so, strafe left or right. its the flame jet thingy that'll do fire damage and shoots you up so...strafe!
I'm glad they added/fixed the cast bar. For the record, we got Maloriak down before the fix, but now with the cast bar it's a LOT more clear when and where he's doing the flame jets. Simply relying on an animation with no other warning makes it a lot more difficult to time and react for positioning, so that guy who said no cast bar doesn't know what he's talking about. That's like trying to interrupt a cast that has no cast bar. It's a faulty mechanic to the fight.