Game 1 Necron v SM
This is a nice display of SM aggression - but badly directed.
If you go for 4 scouts - either you commit to harassment with multi-scouts or capture the map. Not try to do both and send 1 squad over to try and kill a scarab squad. That will not work. Once the early stages offensive did not work out, the SM player did not bother to pull back and try a different plan.
The attrition battle will never favor SM. In fact, a lot of resources were not captured with the idling scouts. Necrons sensing no threat simply absorbed the blows and hits Tier 2 to finish the game. SM is too far behind to catch up.
Game 2 Tau vs DE
I'm pretty shocked DE would lose. But then again they're always the master of short engagements. The longer they spend time in fights, the worse it gets. And it showed when they stubbornly stuck to fighting under the Tau LP2.
They should really switch targets, especially when Hellions can simply jump away when the odds are against them. A case of bad risk assessment perhaps. DE did not capture their side of the map either and Tau pulled ahead once they hit T2.
Game 3 Tau vs Necron
This is a weird game. Necrons were pushing Tau hard in T1.5 but backed off once Tau deploys T2 Vehicle - I did say Skyray was a bad choice because what Tau needed is more mobility vs Necrons. Devilfish transports will also force Scarabs to play detectors. Anyway, the Tau army composition of 3 Firewarrior Squad and 1 Pathfinder isn't particularly impossible to counter for Necrons. They could deploy flayed ones and the Necron lord with solar pulse artifact - then the entire range advantage would be completely nullified. Especially in Quest Triumph's narrow passage.
But either the Necron player is not aware he can load the Flayed ones back into his monolith for another deep strike or he's simply despairing in the face of a Tau murderball - he resigned with 650 energy in reserves. That's a bit too early, IMO.