Well.... Reinforcement of the Army is Limited for some reason I don't completely understand, but there is most likely a reasonable reason for it.
Probably best to keep the cost of it to "Discard" rather than allow it to tribute as well. Hand advantage is important to balance. As for the card itself.... I'd say either allow it to add only one Warrior or Limit it to 1.
Because combos like Shadow Mist exist with Reinforcements. It's basically the best search for any warrior deck that runs any 4-, ever.