Well, I originally intended to make two very simple points, though in fact the hand turned out to be more interesting than I had thought. So this is going to be a bit of an essay.
The two simple points were:
i) If RHO has singleton D10 or J you have 5 diamond tricks as long as you start with the AQ
ii) There is a standard piece of play advice "when in doubt run your long suit" but here you aren't in doubt and you shouldn't run your long suit.
We've observed that if LHO has led from J98 then they have a heart entry and you need the CQ onside, but if possible we should try and find a line that doesn't depend on the CQ onside, because they might misdefend (or LHO might have led the 8 from 98x or 8xx or something asystemic). We also should endeavour not to go off when diamonds are 3-2.
If diamonds break, we have 5 diamond tricks, 1 heart and two spades - plenty, except that they have 4 hearts and 2 aces first. If they don't break, we'll need to take a club finesse as well.
How can it hurt to play diamonds first?
If we take the A and K or the K and Q (as suggested), keeping a top honour in hand, and play a spade, then even if diamonds are 3-2 we are going to be in trouble. We have to find 3 discards from dummy and 2 discards from hand, and keep sufficient entries to cash the top diamond and get back to dummy. If you work it through you'll find we have to discard two diamond winners from dummy and are back needing the club finesse. So we can't do that.
If we start by taking the AQ of diamonds only, then play a spade, RHO may be able to win the first spade and cash hearts. We can discard one club from dummy, but will then be stuck if RHO can return the third diamond, as Trumpace pointed out.
What about this possble club finesse? Suppose we take the AQ of diamonds and RHO shows out (without singleton J or 10). If RHO has J10xx he can play another diamond when he's in and will have 7 tricks before we do, but LHO might have J10xx. Now we run the jack of clubs to RHO's ace? If LHO covers, RHO can play a club back and we'll need to guess immediately if he has the 9 of clubs (finesse) or a doubleton (rise). Gulp. No, we don't want to do that yet, so we can play a spade: we know we can always get back to hand with the king of spades. So spade to the Queen ducked... but we'd better take the DK now we're here or we'll never make it.... and we're off if RHO had Jxxx or 10xxx because he'll be able to cash it (whereas before we'd kept hold of the tenace in dummy). Second spade taken, hearts cashed. Dummy discards a club and 2 diamonds, hand discards two clubs and we are just about OK as long as RHO was exactly 3514.
Now suppose diamonds are 3-2 all along. What if we cash all 5 diamonds discarding hearts from hand? We then play a spade, RHo will win and cash hearts. We'll have played 5 diamond tricks, 5 heart tricks and a spade in total, so dummy and hand each come down to 2 cards. Dummy must keep Kx of clubs, so hand will have a spade honour. Better make sure we keep the SKx in hand as we run diamonds.
So we can survive by starting with the AQ of diamonds as long as we are really, really careful later on.
But the point of this hand was that you can avoid the need to be really, really careful later on if you simply don't touch diamonds. Play a spade towards dummy at trick 2. If that is taken, you can discard a club, a diamond and a spade from dummy and two clubs from hand with no problems at all. If that is ducked, play the AQ of diamonds. If they come in you have 7 tricks. If they don't, cash the AKQ of diamonds and play a second spade honour from dummy, planning to take the club finesse eventually.
We can avoid the need to be careful by setting up our 7 tricks early. At the table, declarer wasn't careful:
He won the opening heart lead with the Queen, and ran five rounds of diamonds, discarding two spades from hand. Oops. He then played a spade off dummy, and RHO rose with the ace. On the last heart dummy had to discard from the queen of spades and Kx of clubs, and he had to guess what RHO's 13th card was. He decided RHO had come down to Ax of clubs, discarded the SQ from dummy, and East's 7 of spades was the setting trick.
1♥ P P x
P 1NT all pass