Attempted Saryrn a few days ago. It was a simple tank-and-burn fight. This is how I recall it.
1. Rampage - She has wild rampage which is difficult for melee dps to avoid, even at max melee distance. Fortunately, it's not as bad as Grummus' rampage. Seems to be slightly mitigated.
2. Melee output - I didn't tank her personally, but the WAR who did reported that he was hit for over 4k in defensive. I think he was close to 4k buffed at the time. He said he did not notice any flurries, but she did quad.
3. AEs - She casts some kind of short ranged ae stun, which is easily resisted if you have high stun resist. At 665 resists, I resisted it 1/3 of the time. She seems to cast it once every minute.
4. Tanking - There are two cubby/corners to her sides from her spawn point. The main tank should shrink and corner tank her into one of them.
5. Adds - Adds (those mouth things) seem to spawn at 75%. Their dps and hp were not scaled with Fabled Saryrn, which makes them easy to control. Sorrowsong spawns later, but he's easy to deal with also.
6. Loots - Drops 3 pieces of fabled items. Got two cloaks and one earring.