I really think that they meant the volcano thralls to have 15 accuracy and 2 survival instead of the other way around. That would essentially make them the most well rounded but not best in any class thrall. Mind you looking at the data for thralls and across factions, there are several glaring errors in the stat/health distribution.
I put a spreadsheet together, and have a post in the Players Helping Players thread that explains more about it and possible errors.