A lot of Summoners seem to think Contagion is the end all be all of pet abilities, and it's quite easy to see why:

+15 seconds to dots = 5 extra ticks per dot
Tick of Bio II + Miasma + Thunder + Bio = 145 potency
145p x 5 = 725 potency per cast time

725ppct, that's a big number, far bigger than any other Summoner ability, but the math isn't quite that simple. Essentially, there's an opportunity cost for using Contagion: it delays when you would normally be able to recast your higher ppct spells (dots) and replaces that time with a period of casting lower ppct spells, 6 globals to be exact. So the ppct of Contagion isn't 725, but rather how much damage the Summoner can do in those 6 extra globals.

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