Especially when the appearance in "Future Imperfect" was merely the result of Riker remembering the face and therefore including it in his fantasy...
That Tomalak would be involved in three separate confrontations with the E-D might speak of a special assignment. Or then simply of the fact that, just like the Galaxy
class was Starfleet's most potent weapon, the D'deridex
class was the biggest thing in the Romulan arsenal - and relatively few of these expensive units existed, so the odds of the same two facing each other were in fact pretty high.
Add to this that Romulans often operated in pairs to make sure they overpowered their Starfleet counterpart, and you increase the odds of Tomalak being in one
of those warbirds. It would then be rather natural for him rather than his wingman to be the one to contact the old opponent Picard, for psychological advantage.
In contrast, it seemed that Gul Evek always popped up specifically when the Maquis were involved.