Could you give me an example of what you mean? It was my intention that each adventure would have one NPC who the GM could use as a source of exposition and in-flavor team mate, if needed, without being too heavy handed. I thought having NPC allies would add depth to the setting and give the players opportunities for roleplaying. Plus, they can be a source of cohorts if you use Leadership.
Adventure 1 has Torrent to guide the group through Gate Pass.
Adventure 2 has Tiljann to explain the oddities of the Seela.
Adventure 3 has Katrina (mentioned as early as adventure 1) to give the PCs an 'in' with the heads of Seaquen.
Adventure 4 has Balam in case the players are hack and slashers who want an NPC to handle the diplomacy.
Adventure 5 has Three Weeping Ravens (first seen in adventure 3) as a guide to the monastery of two winds (and to provide foreshadowing for adventure 7).
Adventure 6 has the gnomish clan, to give a different twist to the dungeon crawl, and because gnomes are awesome.
Adventure 7 has Fayne, who can guide the heroes through what might be an overwhelmingly large forest, and makes it hard to easily get along with the Shahalesti.
Adventure 8? Well, it has someone who's been in the background for a long while.
Have you played Kingdom Hearts? One of the cool things about it was that whenever you went to a new stage, you got to add a new party member temporarily. Really, for optimal fun, I'd let one of the players play the allied PC, at least in combat.
I'm curious what has you concerned about them.