I came back recently to play, started with the FWL start and found it extremely difficult (console), the Assassin is just an awful mech in it's base config, think I took on 3-4 missions and barely made enough to cover my repairs, sold everything in the end and bought a Hunchie and cleared a few missions solo, that bought me a bit of bank to buy another medium and then we were off. But then, those are actually the most fun parts of the game, currently rolling around with a wealth of SL era heavies and it's just not as much fun.
I initially started at the RoR DLC time point when it came out, but just could not get past the final mission, the attrition was just too much for the small force I'd built up over the missions.