Click me for Spreadsheet with BST AF+3 compared to Summoner AF+2/3
Summary:
Beastmaster has the exact same Accuracy as Summoner: 240 and gets +46 Evasion, -114 Magic Evasion, +7% haste
Beastmaster Pet -149 accuracy, -219 Magic Accuracy, -5% Haste, +70 Attack however SMN get's +26 Bloodpact Damage which will make up for the 70 Attack.
Summoner gets the identical amount of Accuracy but also gets 149 more Accuracy an 219 more Magic Accuracy for the Pet. How does that make any sense?
Someone at SE is not paying attention or simply hates BST. I can't think of any other reason why else they would give BST half the attributes SMN or the rest of the jobs get.