Again , mihawk fleeing from his island wasn't due to him being weak.
Mihawk said they keep swarming the island , he already took out the fleet before them , they are just irritating at this point for him.
Marines only went to mihawk protocol wise , they know sending admiral or seraphim would be loss in firepower of Marines , they can't risk it.
Hence no one was sent , he was asked to surrender instead of fight.
Aramaki was deployed for Weevil. You already know what admirals are for. Mihawk deciamtes seraphim all of them and admirals.