CW does a decent job of mixing it up. I haven't actually encountered the wave of identical Thunderbolts yet. Two or three, maybe, but not eight. Split between two or more waves, perhaps. Thunderbolts are probably the single most common 'Mech I end up encountering on the Inner Sphere side, but it's varied enough that I don't mind. I fight primarily in the trial Cataphract and a Jagermech of my own tinkering (2x AC/20), so I tend to laugh at those Thunderbolts and then murder them when they can't out damage me at close quarters.
Stormcrows, on the other hand, are ****ing everywhere.