As someone with a strong technical and scientific background I could also be convinced (one way or the other), or at least influenced by good solid non-agenda driven genetic evidence. Problem is, any organization funding such a genetic study has, by definition, an agenda, or it would not allocate the funds. I have been too close to "scientific research" data in the past to not be very cautious.
Since such evidence is not at hand, a historical approach has to be taken. I am fascinated by the population data, which appears sound. That a population that large should be "assimilated" into neighboring tribes seem more like an excuse for not knowing precisely what happened than a historical fact. That the previously unknown Celts should suddenly burst onto the scene and appear in history en masse, at the same time and same place that the Northern Israelites disappear is just too coincidenal.