Dark is an end hog, which can impede AoE goodness. Spines/fire is great for farming fire mobs - I love mine - but for normal play I'd recommend Willpower or Invulnerability. Both sets will give you buffs that scale up when fighting larger groups of enemies, making them great for spines. They're also both tough and able to handle a variety of situations.
Shield Defense is a fun set, and the scaling damage buff is incredible. But both my SD brute and scrapper feel squishy. I think they'll shine once I have them IOed out, but while leveling my eyes keep bulging whenever someone gets through my defenses and takes me from 100% to 20% HP. 
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My fire/shield by passed by spines/da for aoe fun
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I'm having the same thoughts about mine.
I love them both (and i've played them both extensively) but for sheer fun i prefer the Fire/SD. Nothing like starting every mob with a build up, shield charge, then a fire sword circle. It is my hands down favorite for obliterating mobs.