How to start, well to be honest thank you for playing one of my favorite champion :)
Welcome to mobafire and giving your build on a champion, always rough at first guide and i know since i am still there.
First off is aesthetics, walls of texts, i had to force read so i could comment efficiently on my opinion since i play Skarner myself and thus can provide feedback on the build itself.
The idea of runeglaive is interesting on Skarner since you are building him hybrid and he has ridiculous scaling on all abilities but i don't really agree. Guinsoo is broken without a doubt in 6.3 and fantastic with Q resets on Skarner no objection here. Although I have strong doubts on the efficiency of lich bane compared to items such as Trinity Force and Iceborn Gauntlet for the sheen passive.
You are building such a squishy Skarner when he shouldn't be, the true fear that Skarner can instill is that the longer he is in a fight the more you see him dishing out massive amount of damage. He can displace people, slow, stun and hit them all within seconds, rinse wash repeat in almost no time. You remove that fear almost entirely simply by making it a one shot burst and run type. Skarner scales off better from AD damage than AP except for his W, secondly his W also needs some max health boost.
To finish off because most of it is the build opinions that building AP is a waste on Skarner, your crystal clear guide leaves me with many questions. Masteries, why those ones over other ones. Same for runes. Skill leveling process and why. Then your application of your build, totally absent, i have not seen anywhere how to apply it other than "Don't miss your E"
Also the true fear of any junglers is doubt, if they don't know where the jungler is, every laner will be careful. The secondary fear is what he can do in his skill set.
You can check out my own Skarner to see why I am opposed to your squishy guide but please let us have a discussion and learn from each other.