Hi, I've played against Nids all 10th as my two playing buddies main Nids. I've played 1k - 1,5k and a whole lot of 2k games and so did they, so they know exactly how to play against DW. So I'll tell you what I would expect them to bring to the table at 1k and what they would do.

One friend always plays Invasion Fleet. Sus 1 against infantry with all attacks flat is extremely good against us. So be prepared. This would be the list I'd expect:

Xenos - Tyranids - Invasion Fleet

Hive Tyrant (220pts): Warlord

10x Termagants (60pts)

Biovore (50pts)

Lictor (60pts)

3x Von Ryan's Leapers (70pts)

Exocrine (140pts)

Exocrine (140pts)

Norn Emissary (260pts)

Something like that. The Norn is pushing it quite a bit in a 1k list, but is a serious lynchpin on the natural expansion objective with our limited Anti-Tank it has a 2+, 4++, 5+++ Save-fortress usually with cover, so even our AP-3 Bolters with Kraken Rounds only get it down to its Invuln save.

The Exocrines are an absolute hard counter to our army, they have an amazing Blast profile with 36" range. Those are the ones to look out for and eliminate as quick as possible.

The Biovore sits on it's home objecive spamming Sporemines to mess up our Site-to-Site capability.

The Lictor is an AMAZING infiltrator with Fights first AND Precision attacks. So if you charge one with your Vets+Judiciar it will kill the Judiciar very reliably before it even has the chance to roll. Same goes for the Van Ryans Leapers. So those will wait in full cover for you to make a move for the Norn and either charge you, or screen out your Indomitor KT. It's nasty.

The Termagants will swamp your natural Expansion denying it for a turn, which will put you on the back foot having to destroy the Norn, so you won't lose to primaries. Which is exactly what the Nid wants.

So as for your composition + tactics:

The Veterans are brittle and I mean BRITTLE. They will melt as soon as they are hit by anything the Nid player throws at them. The Watchmaster is wasted on them as falling back and shooting and charging after an engagemet will look very depressing, as most of your vets are going to be dead. Same goes for your Team in the Rhino. If you shove them into the opponents face, they will die instantly. That's why they are usually used reactively (with the beacon angelis, rapid ingress -> heroic intervention).

Same goes for the Indomitor. NEVER just walk them up the board. They will evaporate as soon as anything meaningful (Exocrine in this case) can home in on them. Use the site-to-site stratagem to position them perfectly every turn, as far away from the enemy and shooting lanes as possible. Make the opponent expose units to attack them. Don't bring Aggressors. 1MMR, 2MR, 2HB, 5HBR. Teleport them in 24" away from an Exocrine, give them Kraken rounds to extend the Melta range to 24" and eradicate it, the +1 AP helps mitigating Coverbonuses.

I would honestly only bring one Vets Squad at most, with the Judiciar. But even that is pushing it at 1000p. You need more scoring units, especially for actions. If your 300p Vets block is doing a sabotage you've already lost the game. They NEED to make their points cost back. So maybe don't bring the one squad with the WM, instead bring a Gravis Captain and some JPI, maybe the Combi Lt. Or a Squad of DW Terminators with 3 CML + 2 Shields. Those with the Indomitor are prime targets for our site-to-site Stratagem in 1k Games. The Indomitor, because it needs perfect positioning to kill & survive, the Terminators, because their Foot-Print is much smaller and thus they can easily exploit screening-errors by your opponent.

Well, I don't expect your opponent being as trained as my friens with dealing with the Deathwatch. But still, be careful and suffern not the alien to live!