Anything can be, and is, seen as rape if it serves the purpose of titillating or agitating. Sometimes it's deliberate even when nothing obviously sexual is involved - say, the android Ash in Alien trying to suffocate Ripley with a rolled-up magazine in an oral rape analogy, or certain instances of a male looming over a female and applying violence, force or coercion (the mind meld in ST6 is often seen from this angle). Sometimes it's just in the dirty minds of the audience, though...
Considering the above examples, we could simply be witnessing a pattern of decreasing novelty. In accordance with the way Auberjonois plays it out, the experience is the most intense in "The Adversary" when it's new to Odo; quite a feeling in "Homefront" where Odo exposes the Leyton Changeling; still somewhat intense in the "second occupation" episodes with the Female Founder; but has lost all its shock value by the time Odo shakes hands with Laas.
I see the Great Link as a composite being. The individual "beings" are really just parts of the greater whole. It's a colony creature similar to BEM from TAS