On this hand, I believe the thinking should go as follows:
There are two ways for declarer to take 10 tricks. Make use of dummy's clubs, or else just take 2 club tricks. If he takes only two clubs he needs 8 more. The hear Ace and the diamond K are 2 of them. Where are the other 6? Three ruffs in dummy, 3 trumps in hand. So that gives two possible ways he can make ten tricks, we have to block both. I think it can be done. Or more precisely, GIB says it can be done and I think I see how.
Mostly I find thinking about such things to be fun. Something like this requires far more time than would ever be allowed, and I am looking at all four hands, but it is a demonstration that thought can help. In simpler situations thought can also help, and with practice maybe it can on some hands be done in a reasonable length of time.
On the shown hand, I think E can beat it as follows: Take the heart K at T1 as he did, and shift to either the J or 9 of Ds. This much Gib shows.
Declarer must win, else he loses two diamonds, the heart and a spade.
So declarer wins the diamond K. Playing three rounds of trump won't work, since E will win the third round and they take some Ds, three in fact. So suppose S wins the diamond K and plays a diamond. E wins the diamond and plays a heart, N wins the A. If declarer tries for three ruffs it won't work: Club to Q, ruff a heart, club to J, ruff a diamond, now declarer is on the board. He still has a red loser in his hand, but he cannot pitch it on a high club because W will ruff. He also cannot ruff back to his hand with the spade 4 because W will over ruff. So he ruffs high back to his hand and then ruffs his remaining loser on the board as E pitches a heart. Everyone has three cards. S has KQ4 in spades, E has A87. A club is led from the board, E trumps low, E gets two spade tricks.
Ok, maybe after S wins the diamond K he leads a heart to the board and then comes off the board with a diamond. E goes up and leads a small spade. This kills the possibility of three ruffs, and I see no way for him to cope.
So I think the diamond play at T2 does it. I have not gone through every variant in detail, but it seems clear that to come to ten tricks he either needs three clubs, and the third club cannot be played before spades are drawn, or he needs two clubs, a heart, a diamond and six spades. With that in mind, I think any approach he tries can be countered.
All it takes is a half hour or so of thought while looking at all four hands!
There are many such hands. The reason I thought the IAC forum would be good for this is that we all, to some extent, know each other. So I thought it could be more relaxed. One could just put something up that might be of interest.
Added: An early thought was that after the D switch, if declarer went up (as he must) and then played another diamond, winning and then playing a small spade would be right. Declarer can cope with this if he reads the situation. He wins in hand, ruffs a D, which leaves E with no Ds. Declarer then leads a spade. He intends to draw trump and run clubs, and the defense cannot stop him from doing so. When E takes his Ace he has no more diamonds to lead, the heart Ace is still on the board, and declarer has adequate transportation via clubs.
Also, if you look at the play as it actually went, the possible result switched back and forth a couple of times. E won the heart . Now declarer can make it: lead a spade to his hand, ruff a heart, lead another spade. Thanks to the 3-3 split and the onside D ace, declarer will be able to draw trump and run clubs. But declarer did not do this, at trick 3 he led a D from the board. Now we are back to where the hand can be beaten.
It is often like this. Players make their best estimates of how the cards lie and what will work. Even the best players cannot see around corners, and so Gib, who peeks, can see that the possible outcome shifts back and forth.