How a slight change could open GLA for a future DPS job

[Argyle_Darkheart]

The important part is to make each DPS unique.

Exactly, and 5 abilities isn't much to work with. For example, WAR and PLD have enitrely different sets of abilities (barring cross-class), and they're still very similar.
Why attach a job to a class that doesn't play to that job's strengths? You'll just end up with an incoherent mess.
If you really want a unique DPS, then it needs its own class and a job that augments its strengths.

As for the Scholar example, yes, it works, but I still think Scholar would've been much better with its own class. However, it works well enough because Arcanist has utility and both healers are designed to be able to do damage. The pet also functions as extra "job abilities," without being convoluted.

By spending hit points, DRK would play a lot different than other DPS.

Maybe, but HP as a resource is fraught with issues (read up on other DRK threads).

Take one class, give it a Shield Oath equivalent and Flash, and it could be a tank right away. Give it Rampart and Sentinel, it could eat a lot of damage. That's only four skills.

This already exists; it's called Paladin. Why bother replicating it?

The "frequent" part is precisely when "someone else" can't. Or when you solo.

Your job would be to DPS. Using the ability weakens your DPS. That's bad design.