If you had troub+fury+mage procs and I had a dirge + some healer that's decent I certainly wouldn't lose in parses. What makes the mage group a good place to be is the haste and IA from illu combined with the troub buffs. Without those it's average at best. Average is a lot better than bad, but let's not confuse it with good.
Sure, you can say Tomb's and COB aren't huge, right? But those two combined will do more than all of your mage procs, plus keep you hasted half the time at least. (More than agitate certainly) Now you add on proc boost from the dirge, skill buffs and whatever your healer gives you and you're ahead. ***
*** I'm assuming 3 set boost on dirge