Every team needs 2 things.
1. They need an initiator to initiate team fights; generally this is top notch CC to disable their best carry or preferably the whole team. A spell that puts the other team out of position is even better, like a Blitz grab or a taunt.
2. They need a main tank to PROTECT your team's carries. Additional off tanks (damage soaks) are good too to eat up more damage, but it isn't absolutely required.
This week's champs -
Ashe - Initiate (YES), Tank (NO)
Blitzcrank - Initiate (YES), Tank (NO) Blitz is a soak (off tank) not main tank
Kassadin - Initiate (NO), Tank (NO)
Sion - Initiate (NO), Tank (NO) Sion is a soak (off tank) not main tank
Soraka - Initiate (NO), Tank (NO)
Veigar - Initiate (NO), Tank (NO)
Zilean - Initiate (NO), Tank (NO)
Nidalee - Initiate (NO), Tank (NO)
Vladimir - Iniitate (NO), Tank (NO) - Vlad is a soak (off tank) not main tank
Miss Fortune - Initiate (NO), Tank (NO)
Riot, this is pretty terrible. Did you put any thought into this weeks rotation whatsoever?