Hell yes. I found this game ages ago, and played it through the website. Its an amazing game, great for those pieces of time where you're bored but don't have much spare time, or just want a game where you can play without worrying about stats, or what to do. When I saw that RotMG was on Kongregate, I had an "Oh F*** Yes!" moment. I give it 4/5 stars, and the time I was supposed to use writing a paper.
An easy way to kill large numbers of monsters (I beat a portion of Sloth, and all of envy with this), is to make a "run the gauntlet". Set up piercing blocks in two walls, facing each other, both at the farthest ends of the build area. When the monsters pour over, almost all of them will be killed by flying arrows. + this so people can see it.