Single Remnant fleets are not too hard, less so than the strongest endgame bounties (or system detachments if you fight factions). Hero battlestation difficulty varies by character and fleet. (I can understand not wanting to max enemy range reduction skills just for the handful of battlestations in the game.)
For a real meat-grinder from anyone, let the fleets stack and fight them all in one extended battle. AI loves to abuse its turtle-and-swarm behavior, which is effective against you when it is just you against all of them.
I tried to kill six Remnant fleets at once with only a skilled Paragon. Paragon kills about two or three fleets worth before the ships decide to abuse kite-and-swarm behavior. Run away from Paragon (as Timid captains do) until they could swarm and kill it. Just like in the simulator. If AI was dumber like pre-0.72, Paragon probably could solo the simulator or extended battles as before.