Bad luck and the fact that these 2 spots spawn random thralls is not helping your case:
- It took me 53 tries in singleplayer to get a T4 on this one position. Pretty sure it is possible for the one on the right as well:
EDIT: The second position wasn’t a lucky one for me, at 253 tries got a t4 cook, at 73 tries got a t4 smelter again.
I would say, you have better chances at getting an useful t4 at pagoda than here. You have a fixed spawn for bearer and cook though so if you are after these 2, then you can keep hunting here and hope for the best.