The fluff for the Ares describes them being used as raiders in Lance (4-Mech) strength. After my experiences, it made me wonder if their suppose to be used that way. Anything goes in battletech though! :D
The pirate factions were still in full swing when the Ares first started appearing (right around late 3135-3136). Most of those who saw the early Ares were pirate factions, Senate Loyalists, or random knights trying to hold everything together, so lone Ares would been hefty challenges for them.