The other card, Mishra, Claimed by Gix doesn't do much in a dragon tribal deck, but it IS just four mana, and it works off attacking creatures, fitting into a low curve deck if you really want the meld
Youre playing with strange cards and unpredictability to keep your opponents off-kilter until you find a way to squeeze out an utterly nonsensical win or go out with a bang
Its also a human, so you can benefit from typal bonuses
That's nice and all, but its really the mana cost that makes Sigarda's Aid a powerhouse in multiple formats
This is especially true for the older cards, as there were very few people counting and opening thousands of booster packs trying to determine the rate
I dont like giving opponents the choice on a card because they will always choose the best option for them, rather than the best option for you