User blog comment:Emptylord/Blogs/Journey to Platinum - ADC Thresh/@comment-3466579-20130926235048/@comment-3974211-20130927000135

His kit allowed him to out-play most of their range or mobility, the same as a melee vs ranged set-up top. Ezreal is actually remarkably easy because--unlike against Blitzcrank--Arcane Shift does not counter the grab-component of Death Sentence and it has Death Leap which allows you to follow. Thresh also have Graves-tier tankiness and a shield, which is great for mitigating harass.

I've beaten Caitlyn many times with Thresh and I don't fully understand why. I would presume it's because her net can be interrupted and if you can dodge her Peacemaker, Caitlyn actually has very poor dueling capabilities. Caitlyn wins lanes by harassing - and Thresh's tankiness and shield allow him to mitigate harass.

I haven't yet been against a Varus, but I imagine he'd be similar to Caitlyn. Varus has poke, but is very vulnerable to crowd control. The thing you say "doesn't lend itself to ADC" is exactly what makes him a strong ADC - he is his own support, but you also have your support throwing in extra CC and extra damage.

His Flay passive is a phenomenal amount of damage - both on every attack, and the full 10-second burst.