"Balance" has a very TOS-first-year feel to it. Just as "Return of the Archons" had a very TWILIGHT ZONE feel to it, and many other first year eps were likewise not-quite in the series' format, it can feel "off" at times.
The quirk was pretty much gone by the end of the first year.
I still enjoy them all. For me, this one's a classic.
One of the interesting things about "Balance", for me, is that the notion of starship weapons is still a little rough here. I subscribed to the in-universe idea that this was peacetime, the Federation had not sustained a direct military attack like this for many years, if ever. So the Enterprise's installed weapons were getting pretty long-in-tooth and their effectiveness and reliability was below par. As we see better application of weapons in subsequent adventures, I took it to mean the Federation got off their duffs and started upgrading starship arsenals.
As for the silly discrepancy of the starship barrages being referred to as "phasers" set to "proximity blast", I just ignore it and consider the weapons used to be torpedoes.
Ironic that Spock makes historical reference to how primitive the warfare of the century-old Earth-Romulan Conflict was, since the cat-and-mouse game fought between the Enterprise was primitive compare with subsequent starship battles fought even within TOS.
The drama on board the Enterprise, especially involving Stiles, was electric. The briefing room scene is among the most memorable in TOS, and has some of the same qualities that can be seen in TORA! TORA! TORA! and MIDWAY, both of which were made after "Balance".
Some may disagree, and I respect their views, but having watched the remastered "Balance" on TV about 5 years ago, I would say the CGI FX saved this particular ep. The old FX were getting pretty long-in-tooth, and the new ones really breathed new life into this old classic.