But thoughtseize isn't tribal?
Also Mutavault and Ooze reprints didn't crush peoples investment in any tangible way. They weren't huge staples. I do see what you mean, but I think thoughtseize is too expensive now to not be printed at a mythic rare, and that's the problem. I don't think wizards wants spells like this in the mythic rare spot. I would look forward to it being reprinted in MM2, but the likelyhood of it being reprinted in Theros seems pretty small imo.
They didn't reprint Noble Hierarch or Crucible of the worlds in MMA either. Just because it's expensive doesn't mean it will be reprinted. I actually think when the price gets this high it actually makes it less likely wizards will reprint it. I think MMA is there to make sure that these cards don't get too much MORE expensive, but that's about it.
Just my 2 cents.