I haven't played an awful lot yet, so I'm no expert, but in my experience a few star destroyers with the right support can get a lot of work done. You seem to be having the same thought with your balanced fleets. Since I've mostly played Empire of the Hand, though, I'll mention a couple of things I've noticed about them: Ascendancies and Chafs make a wonderful combination, so I definitely like your first fleet there. I also like to keep a Phalanx or two in my fleets, in case I need something bigger to give and take damage, but that might not be necessary. I've hardly used Syndics, though, so I don't know how they compare to Ascendancies or which one is preferable. I haven't really noticed Karieks to be all that useful, although you may disagree. I mean, I might keep 2-4 in my fleets, but I use Vigilance Gunships as my primary anti-fighter ships. You might also try Bu'direchs: they're the EotH's Dreadnought. They've got the "maximum firepower" ability or whatever it's called, and I found a few of them can provide good supporting fire behind the Ascendancies and Chafs. Nuruodos are very nice, too, as you've noticed. In my last EotH playthrough I usually kept them as reinforcements, to be brought in to lend a hand in a hurry in case one of my bigger ships was getting swarmed. I had a lot of battles in that playthrough where I was fighting against Remnant/Republic fighter and frigate spam, and if that started to overwhelm one of my Phalanxes, for instance, then I could bring in the Nuruodos right nearby to deliver supporting fire and fighters right where they were needed. Which brings me on to my last point, which is that to me, it felt like the EotH tends to find itself short of fighters in big battles. I mean, they get shittons of Clawcraft at the start of a fight, but in intense battles I often found that my capital ships were dangerously short of fighter support midway through the battle. And against the New Republic and their K-Wings, that was not good at all. I liked to keep a couple of Au'riettes (small carriers) in each of my fleets to help with that: I liked to keep them away from the battle and use them to bring in more fighters.
Again, I'm not trying to tell you what to do; I'm just giving you my 2 cents and some ideas for new things to try.
2.2 is also supposed to bring the Peltast, a sniper-like support destroyer with a big main gun that does a lot of damage. (You can see it in Corey's EotH videos.) I'm looking forward to trying it out and seeing how it fits into my EotH fleets.