Nihilus' fleet effectively destroyed the colony of Katarr, which WAS defended by multiple hammerhead cruisers and was only destroyed by the actions of the Mandalorians and the Jedi Exile sabotaging it.
Multiple Hammerhead Cruisers is not the Republic fleet.
The Jedi Exile and Mandos destroyed one ship. What about the rest of the fleet? Unless Traya's fleet is only one ship...?