So you want to be a tank?

[Phoenicia]

The Dark Knight ... and the highest threat of all three tanks.

Just wanted to point out that that is not true at all. Yes DRK has the highest potency enmity combo, but that doesn't give it the "highest threat" potential. You have to look at how their toolkit works. That said, let's look at DRK's "kit":

1- Power Slash combo is DRK's weakest combo of their 3 options so people avoid reusing it. So it is NOT optimal to reuse. Each PS combo used is a DPS loss.
2- Darkside costs MP and DRKs have to stop doing Power Slash to regain MP. Power Slash with Darkside down is weaker than Butcher's combo with Maim up. Dark Arts need two siphon strike combos each use to get the MP back. Ideally, you alternate your Siphon combos for maximum damage while never touching the PS combo after the threat lead.
3- DRK has no offensive CDs that boost their enmity further. Dark Arts Power Slash adds a multiplier of 1 to it (6.5x) and is not even worth the MP.

Now compared to WAR:

1- Butcher Block is WAR's strongest combo and it is optimal for DPS and aggro to alternate BB once every other combo.
2- Like DRK, WAR loses potential by spamming BB. WAR has incentive to use at least 1 Maim combo every third, and 1 storm eye every other combo. Ideally, you alternate SE with BB for maximum aggro damage.
3- WAR has Unchained (33% more DPS in Defiance) and Berserk (20s of insanity). Also you can't ignore Internal Release.

Simply put, if a WAR "wants" aggro, a DRK will not get it.

The rest of your post is spot on though. It is a good way to put the three tanks in perspective.