Legendary items used to suck in Diablo 3, but the many patches that the game has had over the past year have brought them up to reasonably decent standards, making them well worth equipping.
That being said, many legendaries still suck compared to their rare counterparts, and finding them isn't always as exciting as it should be.
Blizzard designer Travis Day has recognized this as a problem and promises that the studio is doing a lot to make it so that every Legendary will be awesome. (via IncGamers)
Responding to a fan who suggested that unidentified uniques shouldn't reveal what they are ahead of being identified, Day wrote: "It is unfortunate when you see a legendary crossbow, pick it up, and realize its a Hellrack. I’ve got an alternate idea, what if we make all the legendary items good so that you can Actually get excited even if you know it’s a Hellrack?"
The Hellrack isn't a terrible item because of its DPS, but because it lacks bonuses to critical hit damage and attack speed in comparison to other crossbows. It's hard to get excited about a legendary that's mediocre in every regard except for raw damage.