[Raynor]

Though perhaps this explains why they send the wind to dissipate him?

How do you interpret dissipate in this case?

after all, surely if he could, then wouldn't he have smote the Hobbits or somesuch?

We know from Myths Transformed that when Melkor was executed:

Originally Posted by Notes on motives in the Silmarillion, iii, HoME X

When that body was destroyed he was weak and utterly 'houseless', and for that time at a loss and 'unanchored' as it were.

I would say that a similar situation occured with Saruman, who was far less powerful than Melkor, and thus even more severely (and for a longer term) weakened by the loss of his hroa.

Is it possible that it was essential to have a Hroa in order to use language?

It depends on what sort of language; Tolkien differentiates between lambe and tengwesta. Lambe, language, has the same root as lamba, which is the phisical tongue, a relation which rose "from elementary observation of the important part played by the tongue in articulate speaking, and from noticing the peculiarities of individuals, and the soon-developing minor differences in the language of groups and clans", cf. Appendix D, Quendi an Eldar, HoME XI. The eldar also used tengwesta, "a system or code of signs": a lambe is a tengwesta built of sounds. As such, it is most likely that thought transmission used some sort of tengwesta; the root "ten" means to point at, and it is free from any limitation to the kind of signs used.

The possession of a Hroa actually provides some degree of 'protection', an additional barrier of Unwill to prevent the mind from being perceived.

While a hroa does hinder thought transmission, I don't think that, in fact, it serves as a protection, seeing that a hroa weakens a maia's (or vala's) abilities, in which I would include the strength of the unwill - although you may be right. I am thinking of Saruman who let some of his secrets slip to Sauron, while looking in the palantir.