The buff to Reinforcements is nice and all, but is it really enough to make it a competitive skill? Unless I'm forgetting something, there just aren't many crucial Warriors in this game. It might help if they lowered the LP requirement or just removed it altogether. For example, maybe you can use the skill any time, but only once per duel.
On second thought, I guess there's Swift Gaia the Fierce Knight. If you have just one monster in your hand, you can swap it for Gaia, set or activate any Spell/Trap cards you have in your hand, and then summon Gaia without tributes. Could be useful for a more generic beatdown deck.