At a 10% grade it is.

while you seem to be getting some good advice here about gearing down, perhaps even setting up your bike differently the thing I think you are facing right now is a psychological issue.

You've psyched yourself into seeing this hill as a negative experience on your commute and that's why even if you climb it faster it is still feeling like a downer. I have a little cottage in the mountains that sits at 2000' elevation and requires a 700' climb in a mile (about a 12% grade) at the end of every bike ride. I can feel myself thinking about the hill as I'm finishing a long ride and turn it into a positive challenge. Try some visualization techniques. Don't dismiss the power of the imagination. Picture yourself climbing some Col in the tour de France. Imagine the strength it's building in your lungs, your heart, your legs, your stamina- and believe me that kind of intense climbing is a strength builder. If you can make it up that at an average of 5-6 mph you are doing real well so be content with your slow speed. Often with physical exercise it is the exercise that challenges us the most that we most benefit from. Stick to it. Ride that thing and take pride in the challenge.