The Armies of Mirkwood and Lorien

2 silvandecks are powerfull. but i would optimize your version:

• Steward of Gondor to Thranduil he can pay for all spheres with his ability
• hobbitgandalf? i would choose the standart for 2 reason, 1. Sneak Attack 2. galadriels ability (hobitgandalf have no use of it) in fact i would put in Sneak Attack + Gandalf in both decks, they help you drawing cards that is lacking in both
• you lack some green cards, would increase the allies (e.g. Galadhrim Healer and Henamarth Riversong.

mirror+harp is (imo) to expensive for only 1 spiritres per round.

Where Steward of Gondor go can change from game to game, both Thranduil and Galadriel are good choices (but from a couple of test games I prefer Galadriel (to better pay for all the Spirit cards). Remember that Thranduil's ability extends to all of your resources, it's not limited to Thranduil's. Another nice thing is that O Lórien! discount applies to the first ally played that phase, no matter who plays it.

Gandalf is my bad, it was intended to be Gandalf. Sneak Attack could be a good choice too.

There is a bit of starting fixed card draw among (MotK) Legolas and Galadriel, and the Galadhrim Minstrel, Valiant Sacrifice and Daeron's Runes do that too.

Henamarth Riversong is a good addiction, especially for shadow control.

to make a good ratio i would increase the allies up (in the galadrieldeck) else The Tree People could whiff. i prefer at least 20 silvans to make sure The Tree People hit with high probability.

i would discard mirror + harp 1 well warned and 1 host for that