It has high armor values maxed out compared to many IS mediums (as far as I remember at least), putting it on par with fragile heavies and some extra survivability in turn... and it needs it. Mediocre at best hardpoints (lots of decent ones potentially, and not a humanoid knuckle dragger at least, but still...), bad hitboxes that you really need to get used to, to spread damage (and often you won't be at all if flanked) with the twisting necessary that rarely helps as much as some other chassis.
IMHO it comes down to the armor values and overall structure it has, even the arms can be surprisingly high ratings; that said it -needs- it. I wouldn't be surprised if it has the mystery Crab/Marauder super tankiness until c-bill release going for it too
(kidding, kidding). If anything it could use a less flat side profile so you can wiggle-and-spread damage more readily (to somewhere other than the arms so readily) and require less to keep on trucking if using XL, but so be it.
OP though? I'm more worried about running into a Wolverine, Griffin, Laser Enforcer, Cicada or Blackjack by comparison for IS mediums, or a competent Centurion. I think this comes down more to "it's tough to kill, and it kills me. OP" syndrome vs low damage output mechs expecting it to fold like a fragile medium,on a really "meh" level mech than anything else.
It's medium that wants to be a heavy, whereas the Cicada is a medium that wants to be a light. If it wasn't so tanky with those current hit boxes... ow. I think it'd really drop down to "why bother beyond nostaglia" instead of just "Meh with some interesting loadouts."