The truth is that when the batting works (and generally when we bat first) we look an excellent side - but we are prone to losing clusters of wickets in the middle order for not many. That's OK if the top three have made some runs, but if they've gone cheaply we are in trouble. The bowling is OK (but this isn't really a 'bowling' competition in the main), nothing spectacular.
So you are right, it's 'when we are on song' - and that's been a bit hit and miss (no pun intended) this WC.