Hearthpwn

I'm not sure which is the absolute most (Probably Rogue though), but these are the ones that I think do more then the rest.

Handlock - Constantly calculating Hand size for Drake/Mountain and HP for Molten.  Then combining it with current Mana and Play Order to drop the right cards.  Hellfire can be used to (very slightly) complicate the plays as well.

Rogues - Needing to calculate Tinker Oil + Blade Flurry Lethal.  Then often playing with Drake/Thalnos to tweak the numbers even more.  While Prep alters mana.  Combo mechanic adds sequencing into the mix as well.

Freeze Mage - Planning out all future stalls in advance, needs to make sure theres enough mana left over.  Also needs to decide between Alex, Antonitas spam, or just early burn.  Usually has Thalnos running in the calculations as well.  Must consider Ice Blocks in between spells for the final plays.

Druids - Planning out future curve with Wild Growth/Innervates.  Then doing damage calc for FoN+Savage lethal.

Shaman - Playing around your Overload, then your RNG Spells.  Often plays with Drake/Thalnos.  Damage + Positioning of the Flametongue totem (Specifically with Al'kir).  Bloodlust lethal Calculations.

While there are builds like Math Warrior... it isn't common to run into those.  So off the top of my head, these are the ones that came to mind.

rogue/shaman  imo..  rogue coz of combos/spelldmg increase etc. and shaman coz of RNG/overload
about that enrage warrior it isnt that hard to play it (i played tempo warr in the past and there were lots of enrage stuff too) .. sure you will need math but i definetely needed it more when i played rogue