I have been following a number of threads which generally ask what we're doing about Skarner, where the general point of view is that he's difficult to do well on. The short answer is that, generally, I'm watching Skarner very carefully because I don't think his full potential is quite realized yet, at least not widely.
That said, in the short term I DO STRONGLY feel that Skarner's ability to jungle is weaker than I intended. Throughout his development, Skarner was annihilating jungle clear times in extreme safety and I had to make repeated nerfs to bring him in line. We went too far in the opposite direction by the time of his release. I would like improve the safety of Skarner's jungle, without making large impacts to his overall performance outside of it.
A subpoint--he's super-dependent on Blue Buff for any kind of jungling. I'd like to fix that as well--lowering Q's mana cost might be the safest route.
We have also seen how top lane Skarner can be pretty powerful. So we have to be careful with buffs or we'll quickly find ourselves in trouble. His E, which a lot of players find to be sort of "out of place" was in part designed to give him a lane sustain option, and that has worked out as expected here.
There are some common points about Skarner which I would like to address.
"I am frustrated by having to cast Crystal Slash twice before I get a slow off."
The strength of Skarner's "perma-slow" is only excused by the fact that he's got to both close to a target and then stick on them before his slow kicks in. That said, I think Skarner actually just gets away with a lot of power here, as things like Red Buff, Gunblade, or Impale will all give him time to energize himself and start slowing a lot. Flash will still cause you to escape Skarner--but I can't have the goal for balance be "beats flash".
"I am frustrated by losing Crystalline Exoskeleton's benefits when I get attacked."
Similar to the above, the stats you gain are that much higher because of this weakness. Getting AP, Armor, and MR will give you more resiliency here. You also don't need a full duration from this skill for it to be highly beneficial in combat. The strategic movement granted by a the full duration of the buff is also really strong on both Summoner's Rift and Dominion.
"Impale's duration is too short."
After extensive playtests at various numbers here, I chose 1.5 because it most consistently provided satisfaction for Skarner without causing his victim to punch his monitor in frustration. Generally. I agree that R could be longer without making Skarner OP... but does it need to be for this skill to be fun, interesting, and satisfying? If the goal is simply that Skarner overall needs buffs, I wouldn't start here.
"Let me do melee attacks during Impale."
Impale's full value comes from repositioning an enemy. You can't do that while autoattacking that champion, so I force you to give up autoattacks in that time. (Admittedly with a lot of skill you could still move/attack/move to get some movement off but that's trickier than I would like the skill to be and very conflicted.) Similarly, you can't cast E and move so the same reasoning applies. Note that Q and W don't stop movement and are enabled in this time. If I wanted to design a skill where you just cc'd a target and could go to town on that target... well... it would be a different skill from Impale.
"Fracture is a dangling skill, I don't know how to use it."
Fracture was included in part so that Skarner wouldn't be hopeless in lane. He's actually quite good as a top solo lane, dependent on this skill, so I would say mission accomplished. If you focus on Q and W, I won't blame you, I often will level those first myself. 1-point in Fracture also gives you a lot of poking utility in Dominion, and picking it early is one way to go about jungling.
"Let me cast Fracture while moving!"
This has a lot of good reasoning behind it. It's more appropriate for Skarner (and similar champions like Udyr and Renekton) to get instant-cast spells, but Fracture specifically isn't the kind of spell I'd normally make instant-cast. What I specifically don't like is how novice Skarner players will choose to cast E instead of keeping pace on their target, landing the E but giving up a future Q or autoattacks. That feels like a trap to me, so I'm pretty inclined to look for a fix here.
TLDR: Possibilities include buffing Skarner's jungle, lowering mana costs, and allowing you to cast Fracture while moving.