This build Utilizes Thresh's late game tankyness to the max. He is very strong if played right and can have very high burst damage. His early game can be bad and its hard to come back if u get behind but that can be overcome by the help of your team. Hes Q makes for easy gap closing/opening and the passive makes it easy for him to harass and farm. His E plus his Ult make for Insane burst late game/teamfighting.

The rune Page i have for him makes it easy to last hit/harass. They also make him more tanky Which is what this build is trying to do. The mastery page is set up to give u the max Tankyness u can get will still have enough early damage to win against Your lane.

Pros
Lots of cc potential
high burst with ult
Very tanky late game
Very strong if played right

Cons
no armor at low level
hard to use skillshots
needs alot of farm
hard to come back if u get behind

If u have any question just leave a comment and ill get back to u as soon as i can.