Pretty dam fast. only 6 minutes ish.

http://www.youtube.com/watch?v=iMXdZcDj57g

Masteries:
16/3/11
16 - offense to maximize your speed in the jungle
3 - Armor to just tank more in the jungle
11 - Buff Duration + exp = core

Runes:
Atk speed Reds - Reset Cooldowns faster
Armor Yellows - You're Jungling bro
AP Blues - More speed
AD Quints - More Damage

All of the runes can be swapped out for other types of runes if you feel you don't value jungle speed and value more defense or movement speed.

Skarner tears through the jungle.

Which is good, because his ganks are pretty meh without ult.

THIS IS SO SLOW. I've been able to hit under 4 minutes with a full clear of the jungle. Go wolves, blue, wraiths, small golems, red, b. Then either do wolves , wraiths, small golems or gank! Even if you suck at ganking, applying any pressure is needed! ANY PRESSURE. Also, you can "steal" some exp from solo lanes provided it is a little bit, or watch their lanes after a successful gank. Making you reach 6 even faster! Grinding to level 6 is the worst way to do jungle, you need to apply pressure, ANY PRESSURE, no matter how small it is!

While you're correct that early pressure is undervalued (possibly because the average player is not familiar with gank timing and how to apply pressure), I think you also underestimate the value of simply knowing fast, effective methods for reaching level 6.

This speed jungle is not optimal.

Try this:

17-3-10 Masteries
3 AD Quints
7 ArPen Reds
2 AD Reds
Armor Yellows
AD Blues

This minimizes jungle clear time. Here is my speed full-clear jungle from before the Skarner buffs:

http://www.youtube.com/watch?v=J8i_mQdyl7k

If I can full clear in 3:23, you should be able to reach level 6 much faster than 6:20 with the rune and mastery setup I use.