[Closed] Rear derailleur alignment. Is it bent or worn out ?

The rear derailleur on the tandem doesn't look quite right to me.

With the bike upside down and the chain on middle ring at the front and smallest sprocket at the back, the derailleur cage is in line with the chain.
Moving the chain to the biggest sprocket, the cage is angled the opposite way to the chain.

It doesn't really show up in this picture, but what I mean is, shouldn't the cage be parallel to the sprockets, not angled top left to bottom right ?

[img] [/img]

Looked at from this angle, the chain is dragging against the right hand side (as seen here) of the cage.

[img] [/img]

The replaceable derailleur hanger on the frame doesn't appear to be bent.
There's a bit of play in both pivots of the derailleur, the one where it bolts on and the one where the cage mounts.
Even if I take up all the play, it only just about goes straight.

How much misalignment is acceptable ?
How much wear is acceptable in the pivots ?
I thought about just bending the hanger to get it to line up. Is that the normal way of overcoming it ?