Yeah getting the portal up Turn 1 makes most sense to me, especially since I can't thin of any way to make your particular plan more reliable.
Why are you set on him emerging turn 3?
If you deploy the WWP turn 1, you're still ~14" up from your DZ which is quite respectable. Talos emerges Turn 2, moves 6", can't charge anyway, either shoots or runs another 3.5". You're only really losing out on a turn of movement, but your giant smashy spiky T7 3+ monster is already in their face and can move further. That's an extra turn to use his weapons to get that first pain token, or run him to contest or scare appropriate targets.
I dedicate these deaths to Odin Allfather, Spearshaker, One Eye.
Fleet Shadowmaker - Kabal of the Dying Sun; Cult of Marrow Excised; Coven of Lambent Hunger
Sons of the Last Breath - Chaos Space Marines
Host of Shattered Purity - Chaos Daemons