Is Dragonknight sustain really that far ahead?

It’s a useful observation, but one skill compared with a passive doesn’t settle the whole class comparison. Try the same character setup, activity, and resource use for each class, then compare how much support each needs to keep going.

The reported testing points to a possible gap, but it doesn’t show how every build will perform. If you’re deciding what to play, check sustain in the specific setup you care about rather than assuming the result applies everywhere.