Most people here would regard the number 2 CB position as a glaring need.
Gilmore's value to the Pats is at least partly tied to the fact that he's played both boundaries and even the slot at a high level. Such guys are pretty rare. Since the Pats don't play strict boundary coverages constantly, and sometimes play match-ups, that makes Gilmore a huge asset.
The Pats appear to have at least three CB candidates for covering the slot in Dawson, JJ and Rowe. In his first year with the Pats, Rowe alternated with Logan Ryan covering the slot and the right boundary, but Ryan "won" the slot job, ultimately, and Rowe, when healthy, has been adequate* on the right boundary (*meaning he hasn't needed need continuous safety help like Arrington did). When Rowe and Gilmore were out last season, JJ played some slot, some match-up and some right boundary, and was equal to, or better than Rowe in all those roles most of the time (his lack of height notwithstanding). IIRC, JMac has played at least SOME on the right side during his career. Cy Jones played virtually all of his very limited boundary coverage snaps in 2016 and 2017 Camp on the right boundary.
CBs who can cover the right boundary adequately aren't particularly plentiful, and guys who can lock that side down on their own are very rare. The Pats have sometimes had difficulty finding CBs who are even adequate on the right boundary.
So, it seems to me that the Pats are evaluating the CBs in Camp for their overall coverage chops in various roles, including being able to cover the right boundary at least adequately. In addition to JJ, Rowe and JMac, they have Lewis, Jackson and Crossen.
One of the drawbacks of media reports from Camp on what CBs are doing is that the reporters rarely note which boundary a prospect is playing when he makes a great play or gets beat in 11 v 11 work. This is either because they aren't aware of the significance of a guy being able to play the right boundary, and/or don't care. So, we really won't know what roles these candidates are succeeding/failing at until we see them in pre-season games.
We also won't know much about their edge-contain, run support or tackling abilities until then, since that's another very critical aspect of CB play that the media guys fail to report. However, we do know that JJ is pretty good at that, and Rowe not so much.
Anyway, I really don't know yet whether the second boundary CB is a "glaring need" or not. During the game tomorrow night, we may discover that the Pats have 2-3 guys who are at least adequate covering the right boundary, or we could discover they have zero.