I don’t think it’s better- The problem is that it’s more unstable: in best case you get out a savanah highmane – but it will much more likely summon an animal companion, 3/3 wolf from flanking strike, a hound or the hyena from highmane.

You can replace Cairne with a second animal companion og spiderbomb. Whether it’s worth crafting spirit singer umbra is a matter of perspective: It’s a great card that you can use in several decks, but the disadvantage is that it will rotate out next spring.

But Houndmaster will weaken your Boom-Zooka

It’s possible, but it will weaken the deck since Kathrena is such a powerful card. You can consider: houndmaster shaw, second animal companion or Spiderbomb.

yes! it doesn’t deal damage, but you still gets the 5/5 minion.