In ranked games there is draft mode now, i think we can see who is playing against us to counter enemies, so what champs are good against what?

there's also some items that help :
tanks : madreds, deathfire grasp

deathfire grasp : only realy works on AP champs, but do please concider you could put it on hybrids such as : nidalee, akali and kayle with a fairly strong effect. (its an active item that does damage equal to 30% of the targets current HP + 3,5% for every 100Xtra ability power you have.) offcourse magic resist helps against this.

Madreds : on a fast hitting DPS this thing is killer, doing 4% of the targets maximum HP as damage.

also currently i am trying the effect of a blade of the divine as an anti tank item (100Xtra magical damage every 3rd hit)

vs dissables : i mostly carry cleanse with me, obviously especially in ranked, but you could always buy a banshee's and / or a quick silver sash (negate the effect and damage of one spell [target spells and skillshots only i beleive] and cleanse negative effects right off of you with quick silver)

also! wards for the win, be sure to use a LOT or get a wriggles lantern (which worked realy well on akali, seeing as i mostly go for a 10Atk sword, and that nicely goes into a wrigles) map control is killer, because if you can catch 1 champ off guard....its one champ less to worry about for a minute =)

i know its not realy champs, but the items and buffs in the game, allows your team even when poorly picked; to play addaptive and increase your chances.