I like your idea for Legolas. It would make sense because Legolas is very skilled at Archery, meaning that his advice would be useful to archers around. I think it should also make Archers gain more experience than usual on kills, making somewhat of a compromise for the people who like Train Archers.
On the other hand, I don't agree on Haldir's ability. It sounds really similar to Rohan's Spellbook power, and I don't think having 2 summons is a good idea. Concerning his ability that makes a unit invisible for a short time, I don't have much experience with the ability, I'd have to try it out more before I can say I want a change to it.
I like the Border Guards summon. While they are not that strong and can't be moved at will, they r always invisible, immune to trample, and there is no limit to how many you can have. If you lucky with Mirror of Galadriel and get Gold (and are not spamming Golden Arrow), the summon spell comes back really fast. They might need a small stat boost though, because they might be a little weak considering that Haldir needs to be lvl 8 to get the ability.