1. It does nothing the turn it comes out.
This may be true but just because they play a 5 drop dragon doesn't mean the game is over. Besides it exerts to use the ability so that's a whole turn that their
glorybringer is a sitting duck. Heck YOUR turn five you could give their dragon its
final reward and it's out of your hair.
2. You want to cast on curve.
Also keep in mind the deck build. Say you had
pyramid of the pantheon on turn 1 and you were able to get it up to 3 brick counters by turn 4. That means turn 5 when you go to use it you'll have 8 mana available if you have not missed any land drops. So theoretically you could cast this card turns later and it will still be relevant when you start making creature tokens in mass or simply making embalmed creature zombies.
Vizier of many faces and
heart-piercer manticore would be
dangerous when making multi copies of their tokens. Hint Hint, if you sac a 4 power creature for the manticore then their dragon is
gone.
3.
Wayward servant and
diregraf colossus dependent.
As stated in the previous point I just made, you don't have to have a mass token engine themed deck in order to get value out of the card. Since a lot of the creatures that have embalm are in other colors you have the ability to run various color decks and you'd always have a trick up your sleeve that no one would expect. I guess that's why this card may be better than you think, if no one THINKS that its a good card then there'll be more room for people to use it creatively and in an unseen manner.