User blog comment:Deshiba/Twitch - Tweaked/@comment-8506165-20140328115610

Just so you know, changing Deadly Venom to magic damage doesn't suddenly make it proc Liandry's burn: has AP-scaling on-hit magic damage but that doesn't proc Liandry's (thank god, can you imagine Teemo with on-hit Liandry's?). And hell, if you really wanted you could build Liandry's on and his W and R would proc it because it just triggers on spell damage regardless of the nature of the damage. If you're just referring to the MPen though, sure, this helps AP Twitch with that.

The damage shift from true damage to scaling phys/magic damage has perhaps overcooked the damage compensation - it's a nerf until he gets Void Staff or Last Whisper in likelihood, but lategame with 39% pen (6% masteries, 35% VS/LW) it's better even against targets with 150(!) Ar/MR. Admittedly, AD Twitch will fare worse against Sunfire/Randuin's stackers now, but in all other cases it's at the very least a late game buff. Particularly given the faster stack application with W. Earlier... not sure, but probably worse. Definitely worse at level 1. Don't know if that's what you were aiming for or not, but there's the numbers for you.

The ult is just a straight-up buff for AD Twitch. I don't know if you meant to do that or not, given that you only intended to open up AP Twitch with this rework (although I'll be honest, I'm not sure why...) but a 10% AD increase more than makes up for the loss of flat AD assuming only 230 bonus AD and his base, plus masteries and runes. Unless it's BotRK Twitch, I suppose, but... the 50 range increase probably tips it back into being a buff for him too.

Just a few thoughts for you to consider. I'm still not sure AP Twitch would be very good even with this rework though, in all honesty - over half the AP scalings in his kit are packed into a physical damage nuke, meaning that his only sources of magic damage are his passive and W, along with any items he builds. He'd probably function, but I can only really see it being as a squishy-killer, particularly with recent Lich Bane nerfs. Against anyone with a modicum of tankiness he'd probably be reduced to throwing venom in their face and hopefully stealthing away.