I think the first fatal flaw in your thought process, and many other posters as well, is that with absolutely no no backing, so many people claim to know lore.

Unless you can link this to some FFXIV lore, I call shannannagins. I don't care what happened in FFXI, FFV, FFVI, FFVII, FVIII, or any other FF series game. At no point has a dev or anyone else "in the know" stated one games lore applies to this one.

Now I admit, I see the point you are making, as well as the lgic behind it. As far as the WHM/BLM link to conjurer, I see that. I do not see the link between WHM and THM at all. Having done all the quest related to THM quest. Now your whole "process of elimination" theory only holds water in your mind. Your pigeon holing the devs options as many are. I admit I am appauled by the amount of people trying to limit the devs only options of game development to making FFXI - 2.

THM could be a necromancer, or a blue mage. They already take from mobs in the form of taps, absorbs, and siphons. Its reasonable to allow the idea of them absorbing abilities as well. Shaman is am option for both classes.

Now I am not saying as a whole, that you are either wrong or right. I am simply saying that by claiming the devs only have the option of either WHM or BLM is where the fatal flaw lies. I personally feel that all too many are pigeon holing there options, by claiming lore this or lore that. I would like to see people actually know FFXIV lore before they use it, because there isn't much of it out there yet, oddly that doesn't stop people from claiming to know it, use it, or make it up as they go along.