That was my point as well, not that any specific mech can beat a quad, but that even if we go all out and try to design the perfect Sirocco, can we make one that can out perform a high end Nightstar or Cerberus or Banshee? The construction rules (mainly the lack of crit space) hamper quads, especially assault quads (I don't know if anyone ever ran out of crit space on a Tarantula without trying real hard, or using heavy FF armor maybe). If quads were just a trade of torso twisting for side stepping and mule kicking, and the front legs still had 12 critical spaces in them (before actuators) then I think balance on quads would be closer, and we might say they would be over powered with a boost of some sort. But, I think they are, today, under powered. After all, how many really frightening quads are there? Hellby mentioned the Thunder Stallion, which is scary because its loaded with Clan LRMs and you really can't go badly wrong there. I do genuinely love the Sirocco and I think its a quality mech, but no one has ever gasped in horror when they saw I'd picked one (unless they were really hoping I'd take an Albatross, maybe). I like the Tarantula, but its not meaningfully better than a Spider or Venom or similar. Maybe the Stalking Spider? Some of the PP Scorpions and Goliaths aren't terrible, but I don't call any of them great. Where as there are 95 ton IS mechs and 85 ton Clan mechs that can freeze your blood at their very mention (well, you know what I mean).
I don't propose to change the rules, now. I think quads are perfectly usable (I once wrote a whole article on the topic, in which I concluded that quads have many excellent uses) and their limitations add a fun dimension to the game. But, I think they're far from over powered, and I think that a house rule allowing some quads (perhaps as a design quirk) larger, or different, firing arcs then that could make for an interesting game that would still likely retain good balance (unless perhaps someone set out deliberately to really abuse it, perhaps, which is likely why the rules remain as they are and why I don't object to that).