I feel like it's a lot easier to understand with Forsaken because we know they believed in the Light and had Paladins in life, whereas the precedent for Tauren Paladins was more adjacent to another class so maybe not as obvious, though it was an original faith and take maybe because it was original and less generic it was harder to understand..?
Since the Forsaken would revere and worship the Light in the same manner the Scarlets do as anti-undead zealots, maybe that's easier to understand because the early comparisons are there. A problem I see with that though is unless fallen Scarlets (like Voss was) recruited into the Forsaken due to humanity hunting them down it may be a hard sell for Forsaken to behave like their eternal foe the Scarlet Crusade - though they both already hate the Scourge - but if the Scarlet Crisade is absorbed, then those being Scarlets as outcasts in their own society seems more believable. Hard to imagine who could recruit the Scarlets -- Voss comes to mind as she was one and maybe could prove herself to those Scarlets and has to the Forsaken already.
Might need to think about it more.