Just ignore what the guy before me said. Here is a good answer:
Yes, that skill is quite good actually. It hits fast and hard especially when you have lots of +skills. The most efficient way to use it is to press down the mouse button you bound it to, then move your mouse left and right quickly (from the point of view of your character who's looking at the monsters coming your way). Do that to ensure you spread your damage equally over a wide area. Because the projectiles are still somewhat slow. They don't hit instantly, which means you'll have a delay from when you start attacking to when the projectiles hit. To clear groups of enemies it's best to use that strategy I told you about. If you only charge at 1 line of monsters at a time your clearspeed will drastically decrease. The magic damage is actually quite a lot considering that most enemies don't have any magic resist at all. The other good thing about that skill is that it doesn't have any weapon restriction. So you can easily used a 2-hand weapon for that.
While it may look like it's for single targets, don't get fooled, because it isn't. Whirlpool oskill easily outperforms SMG for static bosses. But if you don't have anything better, it's still okay.
If you can get used to how it plays out, it's not that bad of an AoE clear, especially since it pierces enemies. It's not the best skill though. It doesn't even come close to best farm skills due to its channeling nature (though I don't know how paladin morph reduce the initial charging time before the first missile is released). It's definitely a unique playstyle however.
One more thing: If you get hit, and thus interrupted, you'll have to consider that you won't be able to use it that quickly due to the charging time of around 1 second. But again, that may differ on paladin morph and I have no experience using it on a paladin. I'd also suggest having high amount of HP so you don't get interrupted.
If you like it, use it. If you don't, sell it to someone who wants to try it out.