It can help you decide for yourself for your strategy you can build as many Tribute camps as you want and you can choose one of the 3 factions, but remember that the Tribute camp will not gain resources and doesn't fire arrows, so it is vulnerable to attacks in which you need to defend by units or summon Barricade and I don't think it's easy for a player to build 6 Tribute camps and spam calling since you will be building slave farms for resources as the Tribute camp doesn't gain resources. As I said this will make Mordor more of an offensive as its strategy is to conquer and build Tribute camps, morgul and dol guldor fortress, I think Tribute camps will be very useful since it costs 3000 to build a morgul/dol guldor fortress plus in order for Sauron to use influence he needs to be level 3 which I usually receive by recruiting Cirith Ungol unit and a Nazgul which altogether costs a lot that's why I think instead of Sauron's influence needed for Tribute camp in order to call Unit 2 it's better to make it a power instead. Mordor is lacking in cavalry you only have mountain trolls which cost a lot along with the troll cage and the Haradrim reinforcement power costs 7. Playing against Gondor can be a little hard as Gondor can build cavalry easier and cheaper along with stronger units that can be armed as well. They can spam archers until the building gets level 3 and purchase fire arrows, if you don't have cavalry at this time your toast because the orcs become useless. Gondor's cavalry can be even more cheaper since you can build farms inside the castle or camp, but when playing Mordor you can only build Slaughter houses in settlements or Outpost I think. Not to mention that Gondor has signal fires and can have allies armed and increased which makes them stronger.
I also think that Sauron's influence on Towers should give Barricades fire arrows.