This is perhaps where the game must (partially) deviate from the lore. In the books, the elves in general and Lorien in particular are a peaceful folk who focus (almost?) exclusively on defending their enchanted, timeless home. They engage in war only when they are directly assaulted from Dol-Guldur. In the game, however, what player would want to just sit in his base and defend it throughout the entire game, having no offensive aspect at all? In order to make them enjoyable, you must give them an ability to mount an effective offense, supported as it is in other factions by offensive units, heroes and spells. A faction that can only defend its base will invariably lose.
Specifically speaking, I would give Lorien one offensive and one defensive ultimate spells. If the sunflare is not suitable (on which I agree), maybe replace the animations with something resembling "pure starlight". Perhaps Earendil can come on his ship to punish the enemies of Lorien? I can imagine him like a blue-ish ghostly (resembling Army of the Dead) ship that comes and pours starlight unto enemies (glorified, semi-lore-compatible sunflare basically 
). (I do not know much lore-wise about Lorien so these suggestions might be rubbish. I just want to stress that a strong offensive spell is a must for Lorien, along with corresponding offensive heroes and units. Canon or not, they must be made competitive and enjoyable in comparison to other factions.)
I know that we are still talking about a game, and I thus won't ever expect Lothlórien to just defend its settlement; every faction must have its chances to attack, defend and win.
I just wrote that I don't like very much the offensive characteristic attributed to Lothlórien, since it is a blissful shelter of Joy and Calmness; and the leader of this faction, Galadriel, is also a Hero Supporter hero and her powers are mainly related to enhancement and Protection
The 'offensive' element is more relatable, I personally think, to Mirkwood, since they are wilder and less wiser Elves, and its heroes have a nature and roles much more oriented to fighting; Thranduil is a tank hero, Legolas is mainly a mass slayer and Tauriel is an agile hero.
i think the spell should be like gorthaur s powers of the past ages but instead she becomes dark lady galadriel what do you say ????
I had a quite similar thought some time ago
A spell related to the leader and most powerful hero of the faction; my idea was though a bit different.
It is called something like 'The Last Act of Power' and it obviously involves Galadriel; it refers to her last display of Power/Magic in the Third Age, the destruction of Dol Guldur, and it would also be a powerful enhancement of Galadriel's powers as a Building Destroyer.
The spell gives Galadriel (Galadriel maintains her normal form) an additional and temporary power in her powers set, called in fact 'The Last Act of Power'.
This power has a quite large radius, but it can only be cast on settlements and outposts, and can only be used once.
Galadriel creates with this power a perennial violent Storm on a settlement for almost 25-30 seconds, which will attack (with lightning) mainly structures, but also units; this Storm decreases also all the armour of the structures involved, to facilitate the work for Galadriel or your army in the destruction of the enemy settlement
I recognise, though, that it is an improbable idea and concept, since it is an unique characteristic of Mordor, and it would be kind of redundant using an ultimate spell that remarks Galadriel's powers (even though it would be interesting)
