check this out

In my opinion, some of the effects are overdone and way to apparant. I find myself watching the effects when the overall point of the video is to show gameplay. With that said, the style of effects were pretty interesting and synced with the music well. Kudos for not overusing and abusing slow motion.

 

Agreed with Auburn.

In terms of when to use effects, I quite like when montages save things like camera shake and slow down for a really sick kill. You know when there's a nice triple but then they turn around and pull of a sick no scope for the overkill? Save it for something like that and it highlights awesome kills, as opposed to the use of effects becoming the centre of attention.

Also, I felt like the colour saturation detracted from it, most evident on the shots of Ragnarok. It just ended up looking blurred, so it seemed like a lower quality video than it actually was. I really like how Fragtality did the colour correction in clips like this:

Halo Reach overkill - YouTube

since it highlights the high resolution video rather than detracting from it.

Basically, it seems like you have a really good technical grasp of the effects and software in general, and you also have a great instinct for syncing to the music as Auburn says, just try being a little more restrained in how you use them. Subtle goes a long way in making a real piece of editing art, but this is a good demonstration of your technical skills at the very least, you've got a lot of potential.