Originally Posted by
DotEleven
It says that he is training non-elf undead Dark Rangers, but nowhere does he claim he's taught a ton at large. It's just a new generation. With no accurate number that could easily just be a handful or maybe a small regiment.
There's no reason to have a pure DPS class. Especially as a mail-wearing class where we already have one and the other class is also 2/3rd dps.
As far as thematics the powers of death are getting stronger, so you send in the guy who uses unliving machines that can't really be affected by death magic.
Once again remember, the Death Knights were under the influence of the Lich King. The Dark Rangers are loyal to Sylvanas.
The text does remark Night Elf Sentinels, but that doesn't mean all have been left behind or that the ones left are Dark Rangers. But once again, why then would these Dark Rangers then up and leave to rejoin the Alliance instead of stay with Calia?
Nathanos is literally off to do more work for Sylvanas so no, he's not feeling betrayed. Even if we ignore that, we're once again at "Why would they then also leave the Forsaken to join the Alliance?"