First, criminal juries aren't randomly chosen.
Second, nullification is itself a check, for the power of the state prosecutor. If you think juries are powerful, remember that the prosecutor is more powerful even than the judge: without a decision by this one state employee, the defendant wouldn't even be a defendant.
From what I've read, something like 98% of criminal cases are pled out before a jury is selected. (Trials are expensive and risky for everyone involved.) So the dominant factor in one's fate, by more than an order-of-magnitude, is what charges the prosecutor decides to file.
Nullification, after all, is just one specific instance of a jury verdict: a way for the citizens to point out that the prosecution is without merit. Our justice system is based on the principle of "innocent until proven guilty", so it's quite deliberate that we err on the side of not convicting.
If there is a 5% chance that a juror would unconditionally acquit for a hate crime he agrees with, and even assuming the prosecutor is dumb enough to randomly select jurors, there's still not a 46% chance of acquittal. A single juror can merely hang a jury. The prosecutor could simply try the case again.
What would it take for me to be acquitted for a hate crime because of a bad jury? As a defendant, I'd have to be one of the 2% that would want to risk a jury trial, despite the evidence against me, over the advice of both my lawyer and the prosecutor, and even though most criminal jury trials result in conviction. Then the prosecutor would have to allow a jury to be selected that consisted of 12 people with the same 1-in-20 prejudice as my crime (or fewer than 12, with the remainder willing to be talked into acquittal). I'm sure it's happened, in certain times and places, but these days it looks like it'd be pretty rare.
Not every jury will return the same verdict for the same crime, but that's inherently not a failure of equal justice. (Jury selection would sure be a lot quicker and easier for everybody if we knew that every jury returned exactly the same verdict!) Sometimes juries will make bad decisions, but I haven't heard any proposed system that can yield justice regardless of the people involved. Better to have the possibility of 12 people who can decide to let me go free, than 1 person who can decide to imprison me.
Finally, IANAL, but I don't think that the legislature can legalize marijuana (short of repealing the Controlled Substances Act, which will never happen). It's a Schedule I drug, as declared by the DEA, an agency led by an appointee. It looks like the ACLU is suing the DEA over this matter. I think my state does want to legalize, and my reading of the Constitution indicates that we should have the right to, so in the mean time, nullification seems like a perfect fit here.