D8 called it.
If your chassis is 15 meters tall, having everything high mounted puts you at a severe disadvantage against a 3 meter tall Tank that gets in close.
In game, it gives you a fighting chance against a face hugging Locust. Since we have no infantry or other AFVs other than other mechs, the game gives you little benefit. Occasionally it lets you fire through a truss or building though, on a few maps. Hill humping maps arent the only maps we get.
Now onto the practicality of a mech IRL.
The entire reason for using legs is mobility. Even tracked vehicles require a relatively smooth surface. Legs remove that requirement. That's why we can build steps instead of ramps for your front porch. A properly designed mech would be able to step up above it's own height. Something no wheeled or tracked vehicle is capable of. Then there is fording ability, being able to cross water obstacles without a bridge or time consuming preparations would keep a land army on the offensive at all times regardless of terrain.
Ground pressure, aka sinking into soft ground, is also a non-issue, just like it isnt for you. So what if your mech sinks to it's ankles in mud, it does not stop it from continuing to move, like it would for a tracked vehicle. It may lose some speed, but it wont stop it.
As far as how the weapon systems are designed in battletech, we do deviate from reality a little bit here. Having multiple low powered weapons instead of one ginormous cannon, seems like a bad idea, until you realize how armor works in this future.
Battlemechs have ablative armor. That is armor that gets weaker as you shoot it. Steel does not work this way, so we must assume it's some plastic/ceramic compound. Ceramic plates in today's body armor absorb the blow and spread it out amongst the whole plate, leaving it cracked and fractured. So it may stop one bullet, but likely wont stop a second. So hitting one repeatedly does make sense in this future world. Hence necessitating multiple weapon systems. Though a rapid firing auto-cannon would make more sense logically, like the bushmaster on the Bradley AFV.
When we master legged vehicles, expect them to look like the Scorpion and less like these bipedal tall monsters.