User blog comment:Healingmantra/New attribute for supports/@comment-25281296-20161206160938/@comment-5035765-20161207215157

with your shields example, you aren't taking into account the duration of the shield, which can make a difference. if it's a shield that lasts 5 seconds, you could keep it up constantly with the "100 shield 5 sec CD", but only half the time with the "200 shield 10 sec CD".

But really, Shields are pretty much the worst example to use for this; consider instead Crowd Control. Lets take Janna's Q, Howling Gale for an example: at rank 5 it has a 10 second CD, and knocks up from 0.5-1.25 seconds (depending on how long you charge it). At maximum CDR (45%, if you have the mastery, which you should if you're playing support), its cooldown becomes 5.5 seconds. SO, this becomes a difference between knocking up an enemy for 0.5 seconds every 5.5 seconds/1.25 every 8.5 seconds and knocking up an enemy for 0.5 seconds every 10 seconds/1.25 every 13 seconds... which is kind of a big difference.

CC in general feels stronger the more often it is applied than how strong it is when it is applied (which is part of the reason getting tagged by, like, Frozen Mallet/Rylai's slows a bunch of times in a row feels worse than being hit by Thresh's 99% slow from his ult.)