That is not what he did. As Huth said, Zovaal's stratagem wasn't some very specific thousand stepped plan that needed to work out perfectly. He just kept doing all sorts of things and kept very close watch on everything around so that when something useful popped up he could snatch it and make use of it.
He didn't plan his entire strategy around Argus and us beating Argus. Argus was there and a dangerous "soul" so he had the Nathrezim plant a trap in it so that if Argus got defeated, or was eventually killed by Sargeras after he was done with him (to prevent the Void taking him) or just finally ran out of strength, it would be a weapon that could harm Oribos.
His plan wasn't to make the scourge and LK so that he could get to Sylvanas so that he could get to Anduin so that he could steal the Sigils. He had the Dreadlords convince the Legion to use the LK and Scourge so that he could spread his influence in the mortal realm. The LK was rather useless to him, but when Arthas was killed, Sylvanas happened to show up so he saw another potential pawn to send more souls his way. When Sylvanas fucked up her own gambit, he had her kidnap a bunch of potential people in hopes that maybe one could be used as a puppet to retrieve one or more of the sigils for him.
None of it was his set in stone plan. The set in stone plan was "slowly build up enough strength to break out of the Maw with Denathrius, Helya and Mueh'zala's help, then attack Oribos and the other covenant realms, take their sigils by force and use them to access Zereth Mortis and take control of reality." You'll note that most of this plan was already near completion before Shadowlands even happens. Revendreth is already under his control, Maldraxxus is down to a 3 v 1 war between Houses and about to be under his control and Bastion is at the start of a civil war to fall under his control. All the other tools just speed up that base strategy: deal a blow to the Arbiter to get even more souls, sneak an agent into Bastion to steal the sigil without having to take the whole region, etc.
He didn't need the arbiter gone or Argus' trap to work. He already had anima flowing in en masse from Revendreth. It just sped everything up.
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I don't get why people really want to fight troggs and kobols in Loch Modan... but the lake is back. Or be back in Westfall, WPL or Durotar but they're more green and have nicer textures.
WoD was 'revamp' done right. If you're going to revamp a zone it shouldn't just be HD, it should be entirely novel, with new terrain and a new aesthetic. The barrens shouldn't just be one zone again, it should be entirely overtaken by Botani survivors and a sprawling new parasitic jungle. Westfall but besieged by the Naga with a reef raised from the sea floor at the coast. Tirisfal but it's a toxic wasteland overrun by oozes and slime horrors pouring out of Lordaeron/UC (already a lost cause).