Cards like Thundermaw Hellkite are fantastic threats too, and great finishers, but they rarely do the whole job, they rely on other cards having done a lot of prior work
Knuckles the Echidna One of the best haste creatures in the game, Knuckles the Echidna is pretty lousy as a red commander but very strong in the 99
Smile at Death Smile at Death is an incredible value engine, and being able to get two creatures and even buff them spells doom for your opponents
Goblin Spy, like most goblins, is not very good at his job
You can have up to 15 different lesson cards in your sideboard in BO3, but that wont allow you to have any other regular sideboard cards
You get a lot of good value out of a single card even if you discard cards that are useless at the time, and the elemental tokens go a long way towards making sure you get full value