You might think its overkill, and I'd agree, but I really think that the Imperial fleet would take some very heavy losses and the Viscount could win if the Empire didn't play it right. Why not try the Viscount against fleet of small but powerful ships? Maybe a fleet of, say, 10 Tector star destroyers, 10 Imperial-II star destroyers, and 20 Victory-II star destroyers. I'd suggest ordering both Eclipse and Executor to target the Viscount, so the gunners don't auto target the nearest thing and go for fighters.
Probably wouldn't make a difference, but you never know. I saw some of them firing at the fighters instead of the Viscount. OK, so the gunners on the Eclipse aren't the smartest.