Legionary Assassin parties used to only appear once in my games. Now they come after me repeatedly. I've been attacked three times so far. They also seem to have been beefed up a good deal, carrying Trail Carbines, Thermic Lances and wearing Centurion armor at very early levels. I'm not new to the game by any means but they've become a major annoyance, so...

How do I get them to stop coming after me?

I think we've been attacked about 8 times so far. Since I have 3 companions though, I just think "more loot!" I would think the Legionary ones would stop after you deal with Benny and Caesar wants to see you. I don't know about the other ones.

your going to have to die

Become Ceasar's b*tch... or man up and give 'em what for.

I don't know of any other options.

You could bear the Mark of Caesar and that would stop hostilities.

Honestly, shooting up the CL is your own fault. Whatever happened to live and let live?