Well we did get to see Tomalak somewhat regularly, but his character was never too far developed (and came out downright manic in All Good Things)
A mysterious enemy is great, and the glimpses we saw from the 2 major Romulan Commanders in TOS
were wonderful, as was that provided by Alidar Jarok and the scheme in Data's Day.
Wonderfully creepy and unsettling.
But overall, the more we found out about them, the more conventional they started to become. See Face of the Enemy
. Another ship, another crew, another version of the Obsidian Order or Section 31. It is a tough line to walk between the implacable enemy of The Neutral Zone
and the more commonplace political maneuvering seen in Unification.
I've longed to see more done with the Romulans, but perhaps in many of these cases less was indeed more.
did have a wonderful opportunity with Sub Commander T'Rul to have that recurring character and give a better glimpse to the unique Romulan point of view, unfortunately the character was quickly dropped. Any bts info on if there was a larger plan for the character or why she was never seen again?