The issue is that the floor of the card (when its only making three or four mana) is still way too high, because Dockside is a card that can be looped, reanimated, flickered or cloned to such a degree that simply making an extra treasure or two is still enough to win the game
As your opponents cast spells, theyll trigger Esper Sentinels ability, allowing you to draw a card unless they pay mana equal to the Sentinels power
Trading the ballroom for a bar room, Olivia, Opulent Outlaw leads an army of outlaws, using them to steal Treasure from innocent miners or, more likely, other outlaws
Supply is certainly going to be constrained (how many people came in second place during the Arena League that season?), and demand for such cards must be sparse in kind
A third is to balance the level of aggression in strategies
Outside of this very specific niche, I would expect Aqueduct Rat to be draft chaff