Yeah, Sentry does solo.
By default, going with the most recent version of every character, we'd be dealing with Merged Sentry, who would slap the ***** out of everyone in this battle. Even going with regular Sentry, in 'Annihilation Scourge' you had a team of heralds not being able to hold the Sentry captured for longer than a brief moment.
There is just too much of a power difference, when the Sentry isn't jobbing.