Being able to Proliferate multiple times on the same turn, Inexorable Tide will allow you to give your Creatures huge buffs or take your opponents out of the game in one fell swoop
It also can deal its full payload of damage immediately with much greater consistency in goblins than in other decks making it able to take out bigger things
Part of the power of targeted discard is that it allows you to answer powerful expensive threats (like Approach of the Second Sun or Gifts Ungiven) for a low cost (often a single mana), so in some sense, you are trading up in mana
Legality depends on the tournament format -- Queen Brahne can be legal in some formats and banned or restricted in others
This enables powerful recursion, reanimation, and cost reduction mechanics
Inspired Skypainter in the Prismari deck works on its own, but pairs well with the tokens that Rootha is summoning