Welp, give me a second to tell you about the Stalker... and I promise you'll see the point I'm going to make about the Fafnir.
the Stalker is incredibly tanky with or without quirks.
For years since its inception into the game in 2012, the Stalker with a standard engine can take more abuse than literally any 100 ton mech, in terms of overall damage dealt. This is because 60% of all damage to a destroyed side torso is thrown into the void to never affect the mech, while only the remaining 40% transfers.
Hit by 40 damage to the side torso after its blown off? Only 16 damaged received to the CT.
As such, the Fafnir is perhaps the tankiest 100 ton mech in the game...provided you're using a STANDARD engine. LFE...well that's just your problem. XL? Again your problem.
The real question is this: Is there a variant with CT hardpoints? If so, that's the one to go with. If not, welp...
Maybe you can pull this off in a 1 versus 5. Versus (fresh) LRM Catapult, (fresh) Banshee, (fresh, but helped with) Firestarter, Atlas (battered) and a Jagermech (Caught off guard). March 2014.
The Jager I caught on his own, and later the rest so technically it was only 4 on 1, and you could say the momentary distraction the Firestarter got from someone showing up (and dying) is what allowed me to get rid of the Banshee and the LRM Catapult peppering me from the distance, before leaving me to deal with the Firestarter with only an Autocannon 5 to my name.
On the day of the achievement's patch.
Anyway, my point is... huge side torsos on long mechs can prove to be an additional layer of armor.
Its also a problem... but there in rests the question, better survivability comes at the cost of easily losing huge stashes of weapons...is it worth it?
That's a question only the user can decide.
Its a shame the arms aren't bigger at the shoulders. Then that 40 damage alpha could be reduced to 6.4 damage if it hits just right through the use of torso twisting.
Then again, the Stalker's arms are stubs too, and it was able to do
this
this..
These (also skip to 8:20 for the second epic brawl)
And this one completely solo
And this in a group queue
Because flamer stalker.