The only two drawbacks I can think of in this respect are the lowly 1 toughness compared to Wall making it easier to burn out the way (still offering a 2 for 1...) and that it costs two coloured mana and not one
Youll always choose the more relevant ability for the moment
Nashi, Moon Sages Scion Nashi, Moon Sage's Scion is another mono-black rat ninja like Ink-Eyes, Servant of Oni, but it has a ninjutsu ability that costs 1 mana less and a more valuable combat damage trigger that affects all players rather than just one opponent
At the same time, there are all manner of shenanigans you can get up to when you can put large amounts of +1/+1 counters on a creature every turn
Card design has changed greatly
AVOID EASY WINCONS Every deck needs wincons, but as discussed above, having access to the most efficient wincons like tutoring for Spear of Leonidas for double strike every game isnt really in keeping with Bracket 2