Problems with replacing Ionic spark with Shiv or Tiamat:
Very few of the champs that actually needed an Ionic spark synergize with Shiv or Tiamat, they were generally off-tanks who wanted to push lane and benefited from AS, such as Shen, Volibear and Irelia. However Shiv scales with crits and AS, crits effectiveness increase exponentially with other crits (ie they aren't worth jack until you have multiple crit items as Xyltin stated above when talking about avarice). They also scale more with attack damage. Both of these stats are things that people who actually need to or should buy an aoe item to split push with don't want. Tiamat is the same it scales with AS and flat damage meaning that its weak on the champs that used to buy Ionic spark. ADCs (which this item fits into mostly) don't need split push capacity they should be in team fights and even if they're not, by the time they have all the items to scale up the shivs damage they 1-shot creeps anyway meaning that it barely makes clearing any faster.

TL;DR: Stats and scaling on both Tiamat and Shiv are useless on the majority of champs that its actually a good idea to get the effect on ie split pushers like Shen.

I'm more upset that the replacement doesn't do anything for Volibear, when Ionic Spark was fantastic on him. Poor Voli.

With that said, I believe Hurricane bolts give you 10 stacks for the Shiv as well, so it's a viable on-hit item for ranged units running Hurricane or melee units like Shaco that synergize well with crit and AS.

as long as we have more choices. I'm good with it.

Alright My Opinion on Stattik Shiv? Absolutely amazing when combined with IE and the New Black Cleaver and Hurricane. You get lots of AS to sustein the armor shred of Black Cleaver and you have a bonus to the Crit damage because of IE. You Deal outrageous amounts of damage. And on heroes like kog'maw who does really well with lots of attackspeed you can do crazy amounts of damage and pushing with Shiv.

You use Statikk Shiv for poking and burst.
Its not made for sustained damage, you need to keep in mind that the passive crits when your AA crits so its really 200 magic damage.
This in mind, they need to either buff the stats on this item or buff the passive to do a little more damage, as it is now its a little lackluster.

I agree, I think Ionic Spark is an amazing item, and with introducing like 20 new items in season 3 I don't see why they're taking it out just because it fills some of the role that wit's end does. They say that wit's end is just a better item too but I don't think that's true. In some situations I think Ionic Spark is much better than wit's end.

I still think Ionic Spark shouldn't be removed.

Taimat has changed supposedly to melee only.
Ionic Spark gives some champions the ability to hit multiple targets and do better damage, especially when not stacking AD.

Think of it this way, crit likes more AD whereas AS doesn't care about crit. In other words, champions that that work best with non-AD items can use this to get a bit more magic damage. Attacking 10 times takes at least 4 seconds. Isn't that a huge change from at least 1,6s? But then to say "critical strike!" is like giving a non-AD champion tears.

i want ionic spark back, with the removal of madreds they already hurt my solotop onhit vayne that was so fun to troll around with vs melee only bruisers