The jobs lists on items is a horribly outdated system though and you end up seeing things that jobs should be able to use, but can't or jobs on items that shouldn't have anything to do with them.
Say Oneiros Cappa for a very good example:
Lv.88 Back[All Races]
Def.14 VIT+5
Pet: Physical Damage Taken -3%.
WAR/MNK/RDM/THF/PLD/DRK/BST/BRD/RNG/SAM/NIN/DRG/BLU/COR/DNC
Now this is just one of SE's generic jobs sets that they arbitrarily placed on it and they do this with a lot of gear. Why would this be used on anything other then bst? Where's the pup? Where's the smn? I don't ever see drg pet tanking. There's been other gear where SE has proven they they can make up any combination of jobs sets that they feel like. Like drk placed on something that has the mages set only on it.
Long story short, you have to concider the jobs and not the generic jobs sets.
