Don't give me wrong, but even SCORPION - as of NOW!!! - uses fireballs in Mortal Kombat X. That is not exclusive of Taven's. NRS just loves using fire-based characters. Some of Taven's moves were actually different from the rest of the "fire cast". You pointed out the most generic moves but what about his unique ones? They don't exist? You're simply disregarding them to make your own point valid which to me means very little, sorry... even though I do agree with you in most of your points.
You are right about his fireball and his charge - those were generic yes. Also his fire teleport is nothing special. Now let's deal with his other moves, shall we?
1. The ground pound actually had some twist to it. Its animation allowed you not to be directly affected by combos or projectiles because Taven goes very high above the ground (unless you were in a position you could be damaged that is) and it has potential for more. I've always imagined an enhanced version of it where some sort of lava comes out of the ground once you punch it so your opponent could be damaged up in the air as well. It wasn't a "generic" ground pound. It was still different from Jax's or Sheeva's in MK9 for example.
2. I don't know why you overlooked his three punch move. Not only was it a unique Taven's move as it had tremendously combo potential. It wasn't anything particulary out of this world (yes you could argue that, but neither was Scorpion's scissors in MK2 and yet it is one of its standart moves now), but I also remember that, in certain combos during the konquest mode, Taven could perform a finishing fire punch for bigger damage. This actually would work for his unique-ness in 2.5D MK fighting game.
3. Time control - the sky is the limit here. NRS only needs to use their imagination.
I personally adored Taven's design in Armageddon. He had a more Helenic look, it was completely different from your standart Chinese-influenced designs in Mortal Kombat, but that's just me. Taven definitely has potential for more since he actually does look good and does have some specials moves to improve his gameplay already, so it's not a lost cause. Surely you can see him work much better in a 2.5D MK game than most of the rest 3D cast...