I tested Twister and found out that its cooldown is not the same across platforms.
Flash (fps 60): 17.5 seconds on average (once after every 11 normal attacks)
Mobile (fps 30): 22 seconds on average (once after every 13 normal attacks)
Steam (fps 60): approximately 22 seconds (once after every 13 normal attacks)
Flash (twister - 11 normal attacks - twister)
Steam and mobile (twister - 13 normal attacks - twister)
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I also checked the cooldown of Necromancer Tower's Pestilence.
Flash (fps 60): about 13 seconds on average
Steam (fps 60): approximately 12 seconds
Mobile (fps 30): about 12 seconds on average