Thauherag demon seed vanishingly rare?

[Dracos]

It could be I just went up too fast, but I still see Wretchlings and Fire and Ice imps showing up...

I'm just at the east presently with full ranks (5 class, 7.5 effective) in Demon Seed. I've gotten somewhere between 150-200 seeds. In that time, I've gotten two Thauherag. While for everything else, I've gotten at least a full set so I can see what they might do, I've barely gotten any T4s, and almost none of them have been Thauherag. Since the percentages don't show at all, I have no idea how they're growing and shrinking as increased levels go, but it's just seeming odd to me how uncommon T4s get at maxed level, and how rare entirely Thaureg's are, comparatively, I've gotten almost 3 dozen T5 and T6 ones at this point, enough that I've tossed out piles of ten of them.

Maybe nothing is wrong, but it just seemed a little weird.