this feels like it should be red as double strike is Red/White almost exclusively.

First strike appears mostly in black uncommon because of mirrored knights. I had a picture of a troll with two axes, so I concluded double strike was okay.

While I think the color pie is important (and I think said black knights should be rare), it is true that these kind of "strange" cards exist. Shards of Alara had Goblin Deathraiders, Zendikar had Vampire Hexmage, Mirrodin Besieged has Koth's Courier, etc.

At least I did make sure black didn't get a good double striker like Hearthfire Hobgoblin. Another funny thing is that this set had Florencia, Dark Moonknight as a second black card with double strike, for totally unrelated reasons.

This is probably better than Ridgetop Raptor, one of the two original doublestrike creatures. Black would normally get a 4/2 for ; this is better than a 4/3, especially if there's power-pumping equipment in the set. I think I'd have left its toughness at 2

Remember it's an uncommon. The 3 toughness might have been unnecessary (remember there's Last Gasp, though). There's Uncontrollable Thirst in common, but I think of it as a "cute combo" rather than a serious threat.