I forgot to say you should also hire "snappers". We would have a champ just snapping around the map to make sure all the areas have been wiped out and also so you could hire players who don't have thanatos card. You could pay them like 20 tokens and maybe you can hire 2 one for top and bottom? I mean if you're spending 1000 tokens because you have to keep redoing it, might as well get it right the first time and just hire more people. More people = more time = higher success.
I'd also like to mention that you should reward raiders even if you fail. I've done the raids several times and it's not fun! Please give them something even if you fail. Also, it's fine to fail once since you won't have enough jotnar skull first round anyway. However, if you have to do the raid 4 or 5 times then you're doing something wrong