But are limited jobs really that popular to warrant a 2nd?

I say no.

But Beastmaster can be repurposed to tank. Make their lore be about controlling monsters on the battlefield to keep your allies safe and that only evil Beastmasters enslave monsters to make war. They have a shield already too, so it's not a far stretch.

Granted this negates the whole, have a pet do half the fighting thing, but look at Summoner, they aren't going to do another pet class. Yoshi-p said pet classes are hard to balance too. I feel this is the only way Beastmaster will work for this game is as a tank.