An addition of 5 seconds to the cooldown, a nerf that you could as easily hold for to accomplish on your own, a 5-second decrease to cooldown, or 5 seconds to duration for a whopping 33% increase to whatever amounts to a caster better-than-Trick-Attack on one of the strongest total (personal + indirect) DPS jobs in the game?

I think Contagion needs to be far more reactive, or even not perfectly so (i.e. not even animation delay), but it certainly does not need a even more uptime. At present the only reasons it's not meta-reforming in its own right are Embolden's weird meleephilia and Ranged jobs' abusive marriage to DRG.