Out of 5, and as determined by a shitty Bronze player.

There are three kinds of attributes champions have: poke, sustain, and burst. (EDIT: And peel.) All champions have these attributes (some more than others), but this blog post concerns itself only with supports.

Poke: How effectively a champion can repeatedly damage enemies in-lane without committing to a fight.

Sustain: How effectively a champion can allow itself (or their lane partner) to stay in lane.

Burst: How well a champion can initiate fights and how quickly a champion can kill opponents in all-in fights.

Peel: How well a champion can disengage or stop themselves or another ally from coming under attack.

Disclaimer: Like the champion statistic bars, these numbers are only here to give you a sense of where these champions' strength lies. Also, like the champion statistic bars, these numbers don't mean everything. Thresh is not strictly better than Blitzcrank, for example, just as Diana is not strictly better than Elise for having higher bars in all areas.