Aside from the fact that it's about as fast as a stunned snail, it really does fit with the Clans. It's all about offense. What mech can really threaten it? Face it, it's the perfect area denial mech. Anything that packs the firepower to destroy it has to get in close enough for it's weapons to work. With the Gauszilla, it automatically has a range advantage on anything *not* packing Arrow IVs. Even if the guass misses on half it's shots, in 40 seconds it's put out 150 points of damage. Not many mechs are going to survive that much damage. Oh, and if one of them gets a head hit, it's over.
In a way, it's a Hunchback taken to extremes.
Quite a few can take it, actually. Unless you've got a really good gunner in it, hitting a target at long range is going to be hard- much harder than the return fire numbers. For the cost of a Gausszilla with a 3/4 pilot, you could get a Cougar B with a 1/4 pilot. All the Cougar has to do is make sure it never lets the Gausszilla get less than 16 hexes from it and build up a +3 movement modifier every round- the Gausszilla is looking at needing 10+ to hit if it doesn't move while the Cougar is going to need 7+ to hit most rounds. With target numbers like that, sorry, the Gasszilla isn't going to do well. And that's against a sub-par mech one third its size.