Maybe we kill Sylvanas and it only makes the situation worse somehow. Similarly to how we killed KJ in the Tomb of Sargeras and it only meant going to Argus next. But I do agree I expected a Maw raid to be the penultimate or final one, not what looks to be the second one. In fact I somewhat expected each Covenant would get a themed raid, even if a small one for some, and then the fifth and final raid would be in the Maw, basing myself on the last two expansions featuring five raids total.