you build them just like in SR except replace warmog's by stacking small hp items and get a mix of hp+damage items
prospector's blade, phage+its upgrades, cleaver, zeke's if your team could use it and just a few resist items to get you to 120-150 armor/mr should do (things like spectral lantern, aegis if you feel like it, maw or randuin's). it's no longer viable to get 150-200+ armor/mr thanks to cleaver-a-plenty and every single mother hubbard with haunting guise and sorc shoes running around.
it's always a necessity to have something like 2500++ hp and 100++ ar/mr once you get to level 14++ or else you'll get vaporized in a single stun duration in a teamfight.
you're aiming for something like almost 250-300 total ad, 2700-3000 hp, 120-150 armor/mr for darius by level 16+
I don't play garen much, but you can build some crit on him just to instagib teemo in a single E cast