In the pictures I've created a baseline of what a block action looks like and the most basic variation of a defensive of offensive assist (pics 1, 2 and 3). The attacker is the Skaven Thrower while the target is the Imperial nobility Thrower.   
  
Having said that in picture 4 am I correct in saying that there is only 1 offensive assist, as the top Skaven Lineman and Nobility Bodyguard are marking each other, while the bottom Skaven Lineman is alone, thus able to assist?

Now to ask my question, as the rules state, to offer either a defensive or offensive assist the assisting player needs to be marking the opposition player, while they themselves are not marked by an opponent. As you can see in picture 5 I've added extra players of the outside of the action. My question is, how many offensive and defensive assists should be counted. I count 1 offensive and 1 defensive assist.

To expand the top left bodyguard is marking the top lineman who in turn is marking the imperial thrower, thus they "cancel" each other out, leaving the top right bodyguard as an eligible defensive assist. The bottom most lineman is marking the bottom right bodyguard, thus as I mentioned "cancelling" each other, leaving the other skaven lineman adjacent to the Skaven thrower to be able to give a offensive assist. Is this correct, or are the outer players excluded from the count, and if this is the case then we go to 2 defensive assist and 2 offensive assists, once again canceling out the added strength bonus?

Can't seem to properly understand Block assists, can someone help?