Damn, why so much str, don't the need some agility to move in that stuff?
Well, this comes down to how the game favors str builds. With high str you can also stack IF which means you'll take a LOT of hits in heavy armor.
Not to mention the fact that you can technically swing faster with a strength build. Your actual swing may be slower, but you can turn so much into your swing and not glance that you can hit earlier than other people. You can hilt slash people all day. Not to mention that you can kill a lot of people just by chambering one of their attacks. That's what Wallace did back in the day when he still played regularly. Pretty sure he had 13 ps or so and pretty much never blocked, only chambered. He would 1-hit people left and right. Being slow doesn't matter too much since people have to get close to you to fight you.
You can also rack up a ridiculous amount of kills as a str build just by getting a long, high damage weapon, following a teammate and doing overheads all day.
That being said, agi builds are WAY more fun than str builds.