Yes, if you manage to concentrate skill damage on a single group of stationary enemies, you'll wreck them, hard.
Unfortunately this is very contextual and won't apply to real-world performance most of the time.
This is also the dilemma the devs are facing when trying to balance this I guess...
Only time I enjoy this build (I have the exact same, basically) is at the District Union Center. After the outside bit, and besides the final boss room, every enemy is stuck pretty close together, and spawn from doors that are very close to you, or just all group up when you enter the room. I've switched to a non-hard wired, tons of skill haste and skill dmg build with seekers and stinger hive; Stronghold is damn near a joke with that build. And devs better not nerf cuz its totally situational and barely applicable, but still fun. DON'T TAKE EVERYTHING FUN!