Skarner is like a cross between fighter and tank. He's got less CC than most tanks (all of his hard CC is single target) and less DPS than most fighters. Generally this results in a power curve where his early game is below average, he's strongest at mid-game and then his damage falls off a bit late-game so he either initiates with his Ultimate (Flash + Impale can be lethal) or peels with his E and his passive.
I'm of the opinion that he doesn't need a rework, may not even need any buffs. If they did buff him it should be nothing significant, just small tweaks to improve his functionality (lower CD on his passive proc per target, maybe E applies 2 passive stacks instead of 1 stack, maybe higher ratios on Q).
I'd be interested to know why you (and the OP) think Skarner needs another rework though.