1)Champion - Unlimited actions is really really good lighthouse effect is good against warrior and other effects.
2)Teacher - Works well with non terminal draw to make it draw more and terminal draw to make it non terminal
3)Disciple - Really good gainer self synergizes
4)Warrior - Really powerful attack without the need of other support than other travellers
5)Fugitive - Really helps you get disciple and teacher
6)Soldier - seems pretty lack luster without attacks like margrave or scrying pool
7)Hero - Gold gainers are ok I guess
8)Treasure Hunter - Man, silvers suck in a engine
How does Disciple self-synergize? It's actually an anti-synergy, as you can't gain Traveller upgrades.
It self synergizes by creating higher action density leting you have better targets to disciple.
I think that the lists were not supposed to be about your fav. traveller but more about the best card.
Such a ranking makes halfway sense for the Peasant line, as those parts don't really interact.
The Page line on the other hand is mostly one big thing with Warrior in the middle (as i pointed out). Ranking the cards outside of that organism seems odd to me. For example, TH's Silver gaining stinks. But on a Warrior board, you might(!) want it to get at least one of your Travellers past Warrior. Or, maybe not; because those Silvers slow the exchange down? Either way, looking at those cards in a vacuum is weird. Page itself is the best example why you can't talk about the cards on their own - on its own, Page is nothing. As a chain introducing a Warrior, it's devestating. So it's not about "Which Page upgrade is the best?". It's about, "how do i play a Page strategy (preferrably without getting killed by my co-players for it)?".
This basic problematic also applies for Peasant. I mean, no Teacher without Soldier, right? You wouldn't judge Urchin without considering Mercenary, either. So judging their strength on their own still doesn't make much sense. The only thing you can argue about is the card's strength relative to how hard it is to get them, maybe allowing for a decision on how many of which you want and for which you stop. Allthough, you'd rarely not exchange at all. On the other hand, nobody needs 5 Teachers. That doesn't mean you don't want any. So, "you want Disciple instead of Teacher" isn't really true, and neither is "you want Teacher instead of Disciple". So, well, now you know why i ranked them for their design.
And yup, you are right, that actually makes sense as a self-synergy. Thanks for explaining.