Actually, unless a mech had like super armor, or the mech was gargantuan in size, or something, all it takes is an explosive to one of the legs and the whole thing would fall over. I just have to say, I don't necessarily think return666's comment was insulting, so why would you say something juvenile like "weak in the brain"? Just saying.
But that aside, I'm really digging this design, you did a great job with it. It certainly does look intimidating.
And how is that any different from any other form of combat vehicle? From tank to fighterplane to battle cruiser, one good blast in the treads/engine and it's pretty much out of commision in all cases.
What a mech might lack in direct protection of it's leg, it makes up for it by having the legs in constant motion. One key feature about realistic mechs vs ones from movies/anime or games that gets over looked, is that mechs would never be used in the same way as a treaded tank. It's a supporting system to provide firepower and protection to infantry on the ground in uneven terrain that a treaded tank would never be able to cross.
The C&C3 style attack of a commando planting bombs on the legs would never happen. More likely than not, they'd get stepped on.
You make a good point, however, in the realm of science fiction, you can make up any device to suit whatever story or action you are trying to create. Who's to say a gargantuan mech won't have some sort of defense mechanism? It certainly has the power and space to do it.
I love mechs as much as the next guy, but I have trouble believing in the practicality of them. Tank treads are a much more efficient method of movement compared to legs, and while legs do have more versatility, it just isn't easy to program a system that can take in to account all sorts of obstacles, not to mention the energy required to motorize such movement compared to how easy it is to make a wheel turn.
Of course, in science fiction, we can just say mechs have fusion cores or something.