Greetings,

Am playing the add-on DLC of Seeker, Slayer, etc.
Have beat the second, Naga battle.
I go to the pool, and no new battles.
I select the Naga again and finish again and...
still no new battles...

Any ideas anyone?

That's very strange. I'm assuming you literally mean the 2nd battle (in the 4-battle Rite of Passage), called "Trial of the Naga". IDK what to suggest...have you tried talking to Humaire, who should be standing by the pool? How about going to the other end of the arena and resting? Have you picked up the quest (task?) from the nearby merchant yet? Worse comes to worse, do you have any saves before you entered the arena (maybe still on the island) you can go back to?

Yea, I think I'm glitched or it's a bug.
Am I supposed to defeat the Naga X number of times perhaps?
Otherwise, I'm washing my hands of this tripe...

The only thing I forgot to ask was whether you're in the Beta for turn-based combat. They're still working through bugs and balance changes. If not...and you've tried my other suggestions, then I'm afraid you're glitched. Which is too bad, b/c some of the most challenging fights of the game are in this DLC.

To answer your question, no, you only have to beat any 1 fight 1x.