I think List 1 looks a bit spammy, double Avengers and Double Reapers, then triple Serpents. If you want to try out the new codex I think you need to take as many different units as possible. I think List 3 looks best, however I'd like to suggest you consider a couple of tweaks for it:
-Drop 1 cannon from the Vyper.
+Add a Third Walker.
-Drop one Vauls wrath support battery.
-Drop the lance on the Dragon Serpent.
+Add one more Dark Reaper with starshot missiles.
This will Ld-test optimis the Reapers and the Dragon serpent will still be a very desirable target, so I'd keep it cheap. You will loose a couple of shadow weavers though, whitch I think may be very good against Tau. Blinding them with barrage is nice, since Tau relies heavily on shooting.