Summoner's Ifrit is bad

[Sunako]

Contagion's actual damage contribution can be though of as a nuke that gives you...roughly 1.875 GCDs.

So essentially it's an ability that does 150 potency.

Using this data, you can realize that under RS + pots + whathaveyou, its equivalent to Ifrit using a skill under those conditions as well.

You forget contagion does 0 damage for garuda and it make pretty long delay for next wind blade attack because it have pretty long animation so you are not gaining even that 150 potency and if you have rouse + spur active during you do it, it is even bigger dps lose for garuda. Contagion increase your own dps but it is dps loss for your pet at same time.