Just so there's no ambiguity, and some are thinking I just showed that Lesser Death Aura has a lower MCL (Max Caster Level) in those first shots. Death Aura and Greater Death Aura don't have a MCL anyway so Master of the Dead does nothing.
Well, because I had time. I spent some time farming for a Dragonshard and then swapped the Feat: Master of Death out. So the Max Caster Level on the caster is no longer increasing for Greater Death Aura (GDA) or Death Aura (DA). So if I'm right, with the removal of the Max Caster Level for GDA and DA, we should no longer see any duration increases, and they should actually stay at the same 1 minute 39s, or 99s total given the Caster Level of 25 and the duration calculation for all the Death Auras.
Caster Level: Wizard 20, Epic 5 (from Epic Knowledge x5 at Level 30), Item 3 (Necklace) = 28 Caster Level
Max Caster Level: Wizard 20, Epic 5 (from Epic Knowledge x5 at Level 30) = 25 Max Caster Level
Death Aura duration calculation: 24s base + (3s * Caster Level)
Since Max Caster Level caps the Caster Level at 25, we get the following:
24s base + (25 Caster Level * 3s) = 24 + 75s = 99s
GDA at 99s (1 minute 39s) even though it is being cast at Caster Level 28 (20 Wizard + 5 Epic + 3 Item)
DA at 99s (1 minute 39s) even though it is being cast at Caster Level 28 (20 Wizard + 5 Epic + 3 Item)
And LDA at 99s (1 minute 39s) even though it is being cast at Caster Level 28 (20 Wizard + 5 Epic + 3 Item)
If we look back at my previous post in this thread, with Master of the Dead feat included, we can see that GDA and DA were appropriately having their duration increased when the Caster Level is being boosted further along with the increased Max Caster Level offered by the feat. So it "does" work to allow the boosting of the duration of the Death Auras (by extension of allowing a greater Max Caster Level), so the feat is not broken. Only issue is there's not a lot of ways to increase Caster Levels on Arcane Casters so in most cases the duration increase is not realised or noticed, which is really an issue somewhere else.
J1NG