This was addressed in the Deep Space Nine Companion. In short, the answer to your question is a qualified yes. T'Rul was indeed intended to be a regularly recurring character, coming as part of a package deal with the cloak seen in DS9: The Search.
The producers then decided that they had had insufficient material to justify her presence (especially given that the cloak wasn't going to be used again) and Martha Hackett was released to work on Voyager as Seska.
A few episodes later they did decide to bring back the cloak, but since T'Rul's only real purpose by that point would have been to operate the cloak (and given the unavailability of the actress) the decision was taken to simply replace her with a couple of lines from O'Brien and Dax to show that they know how the cloak works without assistance.
With the mandate that the new vessel would have a cloaking device,
Teleplay Writer Ronald D. Moore contributed one more component to the
Defiant, at least for the season's opening two-parter: a Romulan
crewmember. "We had a notion that we were going to keep the Romulan
engineer on board as a permanent fixture to operate the cloaking
device." Moore says. But the producers quickly realized that the new
character would not offer enough story material to justify making her
permanent. So T'Rul left DS9 after "The Search, Part II" (which left
her alter ego, Actor Martha Hackett, free to sign on to Voyager as the
Ironically, although the producers had fought hard for the right to
install one on the new ship, "by the time we ended the two-parter, we
had given up the cloaking device," laughs Moore. "We thought we
wouldn't ever see it again. It wasn't until a few episodes later that
we decided to say it was still there "
The Deep Space Nine Companion