The principle advantage of Legacy of Serrane was that it provided extra gildar early in the game. Even with this advantage other players considered it to be mediocre.
Seemingly "Aura of Commerce" is and enchantment for 15 mana and 1 mana upkeep that increases gold production of enchanted city by 10%, that is Nice enough in itself, moving "Legacy of Serrane" up to mediocre abilities, or somewhere between mediocre and strong.
In 0.91 with the long lead time to build a bazaar and the need to build: workshop, Tower of Dominion, garden, etc. first, the gildar from Legacy of Serrane doesn't appear until mid-game. At that point it is passe.' Might as well remove it as a strength. It is now irrelevant.
