1) Currently it's so wrong that claiming trolls are only used as battering rams. With the last buff, using trolls is quite mandatory for Mordor players to win. So drafting trolls would be OP for 3 points spell power.
2) It would be unique if Necromancer did not have the similar ability. Besides, he cuts enemy's armor also. It can be switched to spell power but the ability fits with Sauron better imo.
3) Mordor's eye of Sauron, tainted land and Gothmog's leadership already buff orcs around but trolls? I'm not sure. There are several buffs that can be used so adding new one doesn't make so much sense.
I'm the one for keeping arrow volley, it hurts basic units and forces your opponent moving.
In response to your replies.
1) What do you mean Trolls are mandatory for Mordor players to win, I have won plently of games myself using a combination of several different orcs, battering rams, and catapaults. I can understand how trolls could be useful against Rohan and Lorien in terms of their ability to crowd control but most of the time for me, it was a better investment building another income plot or orc barracks instead of wasting it for a troll cage. As for drafting spells being too op, you still would have to pay gold to give Trolls a weapon, if it's too overpowered you can even have it only work on one troll at a time but give it a short cooldown. In general there are a lot of ways the Edain team can balance out the power.
2) In terms of Sauron having a similar ability I can agree with that too an extent, but I do think Wraiths are not utilized enough in the faction considering you have to put in the effort to level up Sauron just to access Wraiths in the first place. And yes there is the Morgul Blade ability that the Nazgul have but under those circumstances you only have one or two Wraiths at a time.
Still if it's not implemented into the game I wouldn't be too bummed about it but I think it's a cool concept.
If you wanted the power to be more unique compared to Sauron's it could be changed to where the power summons a Barrow thats guarded by a couple of wraiths and then disappears soon afterwards, as a more Mordor themed alternative to the old Guard Tower power.
3) Fair enough
In terms of the usefulness of Arrow Volley, I am not saying it's an underpowered Spellbook Power, I am just saying it doesn't fit the theme of Mordor as well as the other powers in its Spellbook.