I think you could play through the WoL campaign without touching at least one sidequest storyline. As long as you do every mission of the other two sidequests, you could still complete enough missions to unlock the main storyline missions and reach Char.
Looks like Blizzard took this as an excuse to make a certain path cannon.
I wished Blizzard would abandon the branching storyline altogether. While it seems cool to have character shows up and interact in non-determined order, it weaken the main narratives. Everything becomes, 3 mission linearly introducing the situation, 15-ish mission going around gathering power (money/essence/factions), and a last 3 mission final showdown. The predictable structure prevent any cool twists or revelation in the other stages. For example, in LotV, the Zeratul twist, happen in mission 2, then a bunch of gathering forces misisons, then it all wrap back to Ulnar for the 2nd twist, then gathering some more forces, then do a final predictable battle with Amon.
@Gradius12: Go
I wished Blizzard would abandon the branching storyline altogether. While it seems cool to have character shows up and interact in non-determined order, it weaken the main narratives. Everything becomes, 3 mission linearly introducing the situation, 15-ish mission going around gathering power (money/essence/factions), and a last 3 mission final showdown. The predictable structure prevent any cool twists or revelation in the other stages. For example, in LotV, the Zeratul twist, happen in mission 2, then a bunch of gathering forces misisons, then it all wrap back to Ulnar for the 2nd twist, then gathering some more forces, then do a final predictable battle with Amon.