This is exactly what Riot said. Sustain being TOO good was the reason spell vamp became unique. However, I do think i needs something. I mean as is it seems really weak and a waste of time.
+25 Attack Damage
+15% Critical Strike Chance

UNIQUE Passive: Your basic attacks inflict Grievous Wounds on enemy champions for 1.5 seconds.

(Grievous wounds reduces healing and regeneration by 50%)

I mean at 1900 gold this hardly seems viable. The grievous wounds is nice. But 25 ad and 15% crit for 1900 and no build options. This is it the end of the line?? Maybe if it built INTO something... but for 1900 gold you might as well buy 4 Doran's Blades for the 320hp 40 AD and 20 hp return on hit. Or wait for 25 more gold and get a Bilgewater.

And if you are THAT desperate for Crit. Then why are you even looking at this item. PD and IE. It isn't like it is an early game buy like the old Executioner's. It is just TOO expensive with no real use. I think they should go the way of Sword of the Divine and just remove it completely until the figure out how to make it good AND fit the role they want it to fill

I concur, but AD casters as we know them simply do not autoattack enough to make the bang for their buck out of the Bloodthirsters lifesteal. They simply put up with its costs for its damage. And considering its cost/AD ratio and common ad caster ad ratios, it's not as viable as all the AP that AP casters get when stacked upon a rabadon's deathcap.

I suppose an AD caster could put up with it and buy a gunblade, but that will not benefit them early or seriously hamper their early game damage.

Really, there is no proper sustain for AD casters, so the (negatively) broken Executioner's Calling seem's like a perfect item to begin with Spell Vamp AD caster type items. It still wouldn't be too enticing for ADcarries as there are too many other more essential options, and AD casters have no real sustain now, except to go in to melee (which most AD casters are) and autoattack.

When we're talking about AD casters, we're not talking about bruisers... but champions (which could be built bruiser, but are sometimes mid and not) like Talon and Zed.

Not melee AD carries like Xin Zhao and Master Yi (Which are actually both better as metagolem bruisers).

Not tanky bruisers with AD ratios like Darius and Olaf (which are also coupled with other true damage and magic damage sources).

But AD Casters with high burst that is most powerfully accessed by stacking AD. They don't have non-suicidal sources of sustain unless they're just so freakishly powerful from idiotic feeding that it doesn't matter if they dunk the entire enemy team.